Quantum dots, a composition or composite including the same, and an electronic device including the same

ABSTRACT

Disclosed are a quantum dot and a quantum dot-polymer composite and a device including the same, wherein the quantum dot includes a semiconductor nanocrystal core including indium (In) and phosphorous (P), a first semiconductor nanocrystal shell disposed on the semiconductor nanocrystal core, the first semiconductor nanocrystal shell including zinc and selenium, and a second semiconductor nanocrystal shell disposed on the first semiconductor nanocrystal shell, the second semiconductor nanocrystal shell including zinc and sulfur, wherein the quantum dot does not include cadmium, wherein in the quantum dot, a mole ratio of sulfur with respect to selenium is less than or equal to about 2.5:1.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of application Ser. No.16/507,406, filed Jul. 10, 2019, which claims priority to and thebenefit of Korean Patent Application No. 10-2018-0151185, filed in theKorean Intellectual Property Office on Nov. 29, 2018, and all thebenefits accruing therefrom under 35 U.S.C. § 119, the content of whichin its entirety is herein incorporated by reference.

BACKGROUND 1. Field

Quantum dots, a composition or composite including same, and anelectronic device including the same are disclosed.

2. Description of the Related Art

Unlike a bulk material, quantum dots (e.g., nano-sized semiconductornanocrystals) may have different energy bandgaps by controlling thesizes and compositions of the quantum dots. Quantum dots may exhibitelectroluminescent and photoluminescent properties. In a colloidalsynthesis, organic materials such as a dispersing agent may coordinate,e.g., be bound, to a surface of the semiconductor nanocrystal during thecrystal growth thereof, and a quantum dot having a controlled size andhaving luminescent properties may be provided. From an environmentalstandpoint, developing a cadmium free quantum dot with improvedluminescent properties is desirable.

SUMMARY

An embodiment provides cadmium free quantum dots that may exhibitimproved photoluminescence properties and enhanced stability.

An embodiment provides a method of producing the cadmium free quantumdots.

An embodiment provides a composition including the cadmium free quantumdot.

An embodiment provides a quantum dot-polymer composite including cadmiumfree quantum dot.

An embodiment provides a layered structure and an electronic deviceincluding the quantum dot-polymer composite.

In an embodiment, a quantum dot includes a semiconductor nanocrystalcore including indium (In) and phosphorous (P), a first semiconductornanocrystal shell disposed on the semiconductor nanocrystal core, thefirst semiconductor nanocrystal shell including zinc and selenium, and asecond semiconductor nanocrystal shell disposed on the firstsemiconductor nanocrystal shell, the second semiconductor nanocrystalshell including zinc and sulfur,

wherein the quantum dot does not include cadmium and

wherein in the quantum dot, a mole ratio of sulfur with respect toselenium (S/Se) is less than or equal to about 2.5:1.

A thickness of the first semiconductor nanocrystal shell may be greaterthan or equal to about 3 monolayers.

A thickness of the second semiconductor nanocrystal shell may be lessthan 0.7 nanometers (nm).

In the quantum dot, a mole ratio of zinc with respect to indium may beless than or equal to about 50:1, less than or equal to about 49:1, lessthan or equal to about 48:1, less than or equal to about 47:1, or lessthan or equal to about 46:1.

In the quantum dot, a mole ratio of zinc with respect to indium may beless than or equal to about 45:1.

In the quantum dot, a mole ratio of zinc with respect to indium may beless than or equal to about 40:1.

In an embodiment, the quantum dot has a photoluminescent peak wavelengthin a range from about 500 nm to about 550 nm, and a molar ratio of zincwith respect to indium may be less than or equal to about 48:1, lessthan or equal to about 47:1, less than or equal to about 46:1, less thanor equal to about 45:1, less than or equal to about 44:1, less than orequal to about 43:1, less than or equal to about 42:1, less than orequal to about 41:1, less than or equal to about 40:1, less than orequal to about 35:1, less than or equal to about 25:1, less than orequal to about 23:1, or less than or equal to about 22:1 (and/or greaterthan or equal to about 5:1, greater than or equal to about 6:1, greaterthan or equal to about 7:1, greater than or equal to about 8:1, greaterthan or equal to about 9:1, greater than or equal to about 10:1, greaterthan or equal to about 20:1, greater than or equal to about 30:1,greater than or equal to about 35:1, greater than or equal to about40:1, or greater than or equal to about 43:1).

In an embodiment, the quantum dot has a photoluminescent (PL) peakwavelength in a range from about 600 nanometers (nm) to about 650 nm,and a molar ratio of zinc with respect to indium may be less than orequal to about 30:1, less than or equal to about 28:1, less than orequal to about 25:1, less than or equal to about 20:1, less than orequal to about 19:1, less than or equal to about 18:1, less than orequal to about 17:1, less than or equal to about 16:1, less than orequal to about less than or equal to about 15:1, less than or equal toabout 14:1, or less than or equal to about 13:1 (and/or greater than orequal to about 3:1, greater than or equal to about 4:1, greater than orequal to about 5:1 or greater than or equal to about 9:1).

In an embodiment, the quantum dot has a photoluminescent peak wavelengthin a range from about 500 nm to about 550 nm, and a molar ratio of thesulfur with respect to the selenium may be greater than or equal toabout 0.05:1, greater than or equal to about 0.07:1, greater than orequal to about 0.1:1, greater than or equal to about 0.2:1, or greaterthan or equal to about 0.3:1 and less than or equal to about 1:1, lessthan or equal to about 0.9:1, or less than or equal to about 0.8:1, lessthan or equal to about 0.7:1, less than or equal to about 0.6:1.

In an embodiment, the quantum dot has a photoluminescent (PL) peakwavelength in a range from about 600 nanometers (nm) to about 650 nm,and a molar ratio of the sulfur with respect to the selenium may begreater than or equal to about 0.1:1, or greater than or equal to about0.2:1 and less than or equal to about 2:1, or less than or equal toabout 1.5.

A thickness of the first semiconductor nanocrystal shell may be greaterthan or equal to about 0.9 nm, greater than or equal to about 1.2 nm,greater than or equal to about 1.5 nm, or greater than or equal to about2 nm.

A thickness of the first semiconductor nanocrystal shell may be lessthan or equal to about 3 nm, less than or equal to about 2.9 nm, lessthan or equal to about 2.8 nm, less than or equal to about 2.7 nm, lessthan or equal to about 2.6 nm, less than or equal to about 2.5 nm, lessthan or equal to about 2.4 nm, less than or equal to about 2.3 nm, lessthan or equal to about 2.2 nm, less than or equal to about 2.1 nm, lessthan or equal to about 2 nm, less than or equal to about 1.9 nm, lessthan or equal to about 1.8 nm, less than or equal to about 1.7 nm, lessthan or equal to about 1.6 nm, less than or equal to about 1.5 nm, orless than or equal to about 1.4 nm.

A thickness of the second semiconductor nanocrystal shell may be lessthan or equal to about 0.6 nm.

A quantum efficiency of the quantum dot may be greater than or equal toabout 65%.

A quantum efficiency of the quantum dot may be greater than or equal toabout 70%.

In an ultraviolet-visible (UV-Vis) absorption spectrum of the quantumdot, a ratio of an absorbance at 450 nm to an absorbance at 350 nm maybe greater than or equal to about 0.08:1.

The semiconductor nanocrystal core may further include zinc.

The first semiconductor nanocrystal shell may not include sulfur.

The first semiconductor nanocrystal shell may be disposed directly on asurface of the semiconductor nanocrystal core.

The second semiconductor nanocrystal shell may be an outermost layer ofthe quantum dot.

The second semiconductor nanocrystal shell may be disposed directly on asurface of the first semiconductor nanocrystal shell.

In an embodiment, the quantum dot has a photoluminescent peak wavelengthin a range from about 500 nm to about 550 nm, and the core may have asize of greater than or equal to about 1 nm and less than or equal toabout 2.7 nm.

In an embodiment, the quantum dot has a photoluminescent (PL) peakwavelength in a range from about 600 nanometers (nm) to about 650 nm,and the core may have a size of greater than or equal to about 2 nm.

The quantum dot may not include an alkane monothiol compound on asurface thereof.

In an embodiment, a composition includes the aforementioned quantum dot,a dispersing agent, and a (organic) solvent. The dispersing agent mayinclude a carboxylic acid group containing binder polymer. Thecomposition may further include a photopolymerizable monomer including acarbon-carbon double bond and optionally a (thermal or photo) initiator.

In an embodiment, a quantum dot-polymer composite includes a polymermatrix and (e.g., a plurality of) the aforementioned quantum dot(s)dispersed in the polymer matrix.

The polymer matrix may include a linear polymer, a crosslinked polymer,or a combination thereof.

The polymer matrix may include a carboxylic acid group containing binderpolymer.

The carboxylic acid group containing binder polymer may include:

a copolymer of a monomer mixture including a first monomer including acarboxylic acid group and a carbon-carbon double bond, a second monomerincluding a carbon-carbon double bond and a hydrophobic moiety and notincluding a carboxylic acid group, and optionally a third monomerincluding a carbon-carbon double bond and a hydrophilic moiety and notincluding a carboxylic acid group;

a multiple aromatic ring-containing polymer including a backbonestructure in which two aromatic rings are bound to a quaternary carbonatom that is a constituent atom of another cyclic moiety in a main chainof the backbone structure, the multiple aromatic ring-containing polymerincluding a carboxylic acid group (—COOH);

or a combination thereof.

The polymer matrix may further include a polymerization product of amonomer combination including a compound including a carbon-carbondouble bond and a (multiple or mono-functional) thiol compound includingat least one (or at least two) thiol group(s) (e.g., at a terminal endof the thiol compound), a metal oxide fine particle, or a combinationthereof.

The quantum dot-polymer composite may be in a form of a patterned film.

When the quantum dot-polymer composite may be in a form of a film havinga thickness of about 6 micrometers (μm), an amount of a quantum dot isless than or equal to about 45% by weight, based on a total weight ofthe composite, and an absorption rate of blue light of a wavelength ofabout 450 nm may be greater than or equal to about 89%.

In an embodiment, a display device includes a light source and a lightemitting element, wherein the light emitting element includes theaforementioned quantum dot-polymer composite and the light source isconfigured to provide the light emitting element with incident light.

The incident light may have a luminescence peak wavelength of about 440nanometers to about 460 nanometers.

In an embodiment, the light emitting element may include a sheetincluding the quantum dot-polymer composite.

In an embodiment, the light emitting element may include a stackedstructure including a substrate and a light emitting layer disposed onthe substrate, wherein the light emitting layer includes a patternincluding the quantum dot-polymer composite.

The pattern may include at least one repeating section configured toemit light at a predetermined wavelength.

The pattern may include a first section configured to emit a firstlight.

The pattern may further include a second section configured to emit asecond light having a center wavelength that is different from a centerwavelength of the first light.

In an embodiment, a method of forming the aforementioned quantum dotincludes:

combining the semiconductor nanocrystal core, a selenium-containingprecursor, a first shell precursor containing zinc, an organic ligand,and an organic solvent to obtain a first mixture;

heating the first mixture to a reaction temperature to obtain a secondmixture comprising a particle comprising the first semiconductornanocrystal shell disposed on the semiconductor nanocrystal core;

combining a sulfur-containing precursor with the second mixture at thereaction temperature to form the second semiconductor nanocrystal shellon the first semiconductor nanocrystal shell and form the quantum dot.

Quantum dots of an embodiment may exhibit improved luminous propertiestogether with enhanced stability. A composition including theaforementioned quantum dots may provide improved processability. Thequantum dots may find uses in various display devices and biologicallabelling (e.g., bio sensor, bio imaging, etc.), a photo detector, asolar cell, a hybrid composite, or the like.

The quantum dots of an embodiment may exhibit enhanced blue lightabsorption, which may find their potential uses in a quantum dot basedphotoluminescent color filter. The photoluminescent color filter may beused in a display device that includes various blue light sources (e.g.,a blue light emitting OLED, a micro LED emitting blue light) and aliquid crystal display device including a blue light source.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a device according to an embodiment;

FIG. 2 is a cross-sectional view of a device according to an embodiment;

FIG. 3 is a cross-sectional view of a device according to an embodiment;

FIG. 4 shows a process of producing a quantum dot-polymer compositepattern using a composition according to an embodiment.

DETAILED DESCRIPTION

Advantages and characteristics of this disclosure, and a method forachieving the same, will become evident referring to the followingexample embodiments together with the drawings attached hereto. However,the embodiments should not be construed as being limited to theembodiments set forth herein. If not defined otherwise, all terms(including technical and scientific terms) in the specification may bedefined as commonly understood by one skilled in the art. The termsdefined in a generally-used dictionary may not be interpreted ideally orexaggeratedly unless clearly defined. In addition, unless explicitlydescribed to the contrary, the word “comprise” and variations such as“comprises” or “comprising” will be understood to imply the inclusion ofstated elements but not the exclusion of any other elements.

Further, the singular includes the plural unless mentioned otherwise.

In the drawings, the thickness of layers, films, panels, regions, etc.,are exaggerated for clarity. Like reference numerals designate likeelements throughout the specification.

It will be understood that when an element such as a layer, film,region, or substrate is referred to as being “on” another element, itcan be directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” another element, there are no intervening elements present.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±10% or 5% of the stated value.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer, or section from another element, component, region, layer, orsection. Thus, “a first element,” “component,” “region,” “layer,” or“section” discussed below could be termed a second element, component,region, layer, or section without departing from the teachings herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

As used herein, unless a definition is otherwise provided, the term“substituted” refers to a compound or a group or a moiety wherein atleast one hydrogen atom thereof is substituted with a substituent. Thesubstituent may include a C1 to C30 alkyl group, a C2 to C30 alkenylgroup, a C2 to C30 alkynyl group, a C6 to C30 aryl group, a C7 to C30alkylaryl group, a C1 to C30 alkoxy group, a C1 to C30 heteroalkylgroup, a C3 to C40 heteroaryl group, a C3 to C30 heteroalkylaryl group,a C3 to C30 cycloalkyl group, a C3 to C15 cycloalkenyl group, a C6 toC30 cycloalkynyl group, a C2 to C30 heterocycloalkyl group, a halogen(—F, —Cl, —Br, or —I), a hydroxy group (—OH), a nitro group (—NO₂), acyano group (—CN), an amino group or amine group (—NRR′, wherein R andR′ are the same or different, and are independently hydrogen or a C1 toC6 alkyl group), an azido group (—N₃), an amidino group (—C(═NH)NH₂), ahydrazino group (—NHNH₂), a hydrazono group (═N(NH₂)), an aldehyde group(—C(═O)H), a carbamoyl group (—C(O)NH₂), a thiol group (—SH), an estergroup (—C(═O)OR, wherein R is a C1 to C6 alkyl group or a C6 to C12 arylgroup), a carboxylic acid group (—COOH) or a salt thereof (—C(═O)OM,wherein M is an organic or inorganic cation), a sulfonic acid group(—SO₃H) or a salt thereof (—SO₃M, wherein M is an organic or inorganiccation), a phosphoric acid group (—PO₃H₂) or a salt thereof (—PO₃MH or—PO₃M₂, wherein M is an organic or inorganic cation), or a combinationthereof.

As used herein, unless a definition is otherwise provided, the term“hetero” refers to a compound or group that includes at least one (e.g.,one to three) heteroatom(s), wherein the heteroatom(s) is eachindependently N, O, S, Si, P, or a combination thereof.

As used herein, unless a definition is otherwise provided, the term“alkylene group” refers to a straight or branched chain, saturatedaliphatic hydrocarbon group having a valence of at least two. Thealkylene group may be optionally substituted with one or moresubstituents.

As used herein, unless a definition is otherwise provided, the term“arylene group” refers to a functional group having a valence of atleast two and formed by the removal of at least two hydrogen atoms fromone or more rings of an aromatic hydrocarbon, wherein the hydrogen atomsmay be removed from the same or different rings (preferably differentrings), each of which rings may be aromatic or nonaromatic. The arylenegroup may be optionally substituted with one or more substituents.

As used herein, unless a definition is otherwise provided, the term“aliphatic hydrocarbon” refers to a C1 to C30 linear or branched alkylgroup, a C2 to C30 linear or branched alkenyl group, or C2 to C30 linearor branched alkynyl group, the term “aromatic hydrocarbon group” refersto a C6 to C30 aryl group or a C2 to C30 heteroaryl group, and the term“alicyclic hydrocarbon group” refers to a C3 to C30 cycloalkyl group, aC3 to C30 cycloalkenyl group, or a C3 to C30 cycloalkynyl group.

As used herein, unless a definition is otherwise provided, the term“(meth)acrylate” refers to acrylate, and/or methacrylate, or acombination thereof. The (meth)acrylate may include a (C1 to C10alkyl)acrylate, a (C1 to C10 alkyl)methacrylate, or a combinationthereof.

As used herein, unless a definition is otherwise provided, “alkoxy”refers to an alkyl group that is linked via an oxygen (i.e., alkyl-O—),for example methoxy, ethoxy, and sec-butyloxy groups.

As used herein, unless a definition is otherwise provided, “alkyl”refers to a straight or branched chain, saturated, monovalenthydrocarbon group (e.g., methyl or hexyl).

As used herein, unless a definition is otherwise provided, “alkynyl”refers to a straight or branched chain, monovalent hydrocarbon grouphaving at least one carbon-carbon triple bond (e.g., ethynyl).

As used herein, unless a definition is otherwise provided, an “amine”group has the general formula —NRR, wherein each R is independentlyhydrogen, a C1-012 alkyl group, a C7-C20 alkylarylene group, a C7-C20arylalkylene group, or a C6-C18 aryl group.

As used herein, unless a definition is otherwise provided, “arene”refers to a hydrocarbon having an aromatic ring, and includes monocyclicand polycyclic hydrocarbons wherein the additional ring(s) of thepolycyclic hydrocarbon may be aromatic or nonaromatic. Specific arenesinclude benzene, naphthalene, toluene, and xylene.

As used herein, unless a definition is otherwise provided, “aromatic”refers to an organic compound or group comprising at least oneunsaturated cyclic group having delocalized pi electrons. The termencompasses both hydrocarbon aromatic compounds and heteroaromaticcompounds.

As used herein, unless a definition is otherwise provided, “aryl” refersto a monovalent hydrocarbon group formed by the removal of one hydrogenatom from one or more rings of an arene (e.g., phenyl or naphthyl).

As used herein, unless a definition is otherwise provided, “arylalkyl”refers to a substituted or unsubstituted aryl group covalently linked toan alkyl group that is linked to a compound (e.g., a benzyl is a C7arylalkyl group).

As used herein, unless a definition is otherwise provided,“cycloalkenyl” refers to a monovalent hydrocarbon group having one ormore rings and one or more carbon-carbon double bond in the ring,wherein all ring members are carbon (e.g., cyclopentyl and cyclohexyl).

As used herein, unless a definition is otherwise provided, “cycloalkyl”refers to a monovalent hydrocarbon group having one or more saturatedrings in which all ring members are carbon (e.g., cyclopentyl andcyclohexyl).

As used herein, unless a definition is otherwise provided,“cycloalkynyl” refers to a stable aliphatic monocyclic or polycyclicgroup having at least one carbon-carbon triple bond, wherein all ringmembers are carbon (e.g., cyclohexynyl).

As used herein, unless a definition is otherwise provided, “ester”refers to a group of the formula —O(C═O)Rx or a group of the formula—(C═O)ORx wherein Rx is C1 to C28 aromatic organic group or aliphaticorganic group. An ester group includes a C2 to C30 ester group, andspecifically a C2 to C18 ester group.

As used herein, unless a definition is otherwise provided, the term“hetero” refers to inclusion of at least one to three heteroatomsselected from, N, O, S, Si, and P.

As used herein, unless a definition is otherwise provided, “heteroalkyl”refers to an alkyl group that comprises at least one heteroatomcovalently bonded to one or more carbon atoms of the alkyl group. Eachheteroatom is independently chosen from nitrogen (N), oxygen (O), sulfur(S), and or phosphorus (P).

As used herein, unless a definition is otherwise provided, “heteroaryl”refers to an aromatic group that comprises at least one heteroatomcovalently bonded to one or more carbon atoms of aromatic ring.

As used herein, a photoconversion efficiency refers to a ratio ofemission light amount of a quantum dot-polymer composite with respect toabsorbed light amount by the composite from incident light (e.g., bluelight). The total light amount (B) of excitation light may be obtainedby integration of a photoluminescence (PL) spectrum of the incidentlight, the PL spectrum of the quantum dot-polymer composite film ismeasured to obtain a dose (A) of light in a green or red lightwavelength region emitted from the quantum dot-polymer composite filmand a dose (B′) of incident light passing through the quantumdot-polymer composite film, and a photoconversion efficiency is obtainedby the following equation:A/(B-B′)×100%=photoconversion efficiency (%)(B-B′)/B×100%=a blue (light) absorption rate of a film (%)

As used herein, unless a definition is otherwise provided, the term“dispersion” refers to a system in which a dispersed phase is a solidand a continuous phase includes a liquid. For example, the term“dispersion” may refer to a colloidal dispersion, wherein the dispersedphase includes particles having a dimension of at least about 1 nm(e.g., at least about 2 nm, at least about 3 nm, or at least about 4 nm)and less than or equal to about several micrometers (μm) (e.g., 2 μm orless, or 1 μm or less).

In the specification, the term “Group” in the term Group III, Group II,or the like refers to a group of the Periodic Table of Elements.

As used herein, “Group I” refers to Group IA and Group IB, and mayinclude Li, Na, K, Rb, and Cs but are not limited thereto.

As used herein, “Group II” refers to Group IIA and a Group IIB, andexamples of the Group II metal may include Cd, Zn, Hg, and Mg, but arenot limited thereto.

As used herein, “Group III” refers to Group IIIA and Group IIIB, andexamples of the Group III metal may include Al, In, Ga, and Tl, but arenot limited thereto.

As used herein, “Group IV” refers to Group IVA and Group IVB, andexamples of the Group IV metal may include Si, Ge, and Sn but are notlimited thereto. As used herein, the term “a metal” may include asemi-metal such as Si.

As used herein, “Group V” refers to Group VA and may include nitrogen,phosphorus, arsenic, antimony, and bismuth but is not limited thereto.

As used herein, “Group VI” refers to Group VIA and may include sulfur,selenium, and tellurium, but is not limited thereto.

As used herein, the term “first absorption peak wavelength” refers to awavelength of a main excitonic peak appearing first from the longestwavelength region of a UV-vis absorption spectrum of a quantum dot(i.e., appearing in the lowest energy region in the UV-Vis absorptionspectrum).

A semiconductor nanocrystal particle (also referred to as a quantum dot)is a nano-sized crystalline material. The semiconductor nanocrystalparticle may have a large surface area per unit volume due to arelatively small size of the semiconductor nanocrystal particle and mayexhibit different characteristics from bulk materials having the samecomposition due to a quantum confinement effect. Quantum dots may absorblight from an excitation source to be excited, and may emit energycorresponding to an energy bandgap of the quantum dots.

The quantum dots have potential applicability in various devices (e.g.,an electronic device) due to unique photoluminescence characteristics ofthe quantum dots.

Quantum dots having properties applicable to an electronic device may becadmium-based. However, cadmium may cause a serious environment/healthproblem and thus is a restricted element. As a type of cadmium freequantum dot, a Group III-V-based nanocrystal has been extensivelyresearched. However, cadmium free quantum dots have technologicaldrawbacks in comparison with cadmium based quantum dots. When thecadmium free quantum dots undergo various processes for being applied toan electronic device, the cadmium free quantum dots may exhibit sharplydeteriorated luminous properties.

For example, for their application in a device, quantum dots often useblue light (e.g., having a wavelength of about 450 nm) as excitationenergy source. The cadmium based quantum dots generally have a highlevel of blue light absorption. However, in the case of cadmium freequantum dots, the absorption strength for blue light (e.g., having awavelength of about 450 nm) may not be not high, which may lead to adecreased brightness.

In a cadmium free quantum dot, introduction of a core-shell structuremay contribute to securing, e.g., providing, a luminous property andstability. For example, an InP based core may be passivated with aZnSe/ZnS shell of an increased thickness to be applied in a quantum dotpattern production. However, the present inventors have found that anincreased thickness of a shell may be desirable to achieve anappropriate level of stability and luminous property while the increasein the shell thickness may also cause a sharp increase in a weight ofeach quantum dot, which may lead to a decrease in the number of quantumdots per a given weight and may cause a decrease in an excitation lightabsorption of a quantum dot-polymer composite.

When the quantum dot is used in a patterned film such as a color filter,the decrease in the excitation light absorption may be a direct cause ofa blue light leakage in a display device, may adversely affect a colorgamut (e.g., a coverage rate under a DCI standard), and may result in adecrease of a luminous efficiency.

The quantum dot of an embodiment may include the structure andcomposition that will be described below and may have enhanced luminousproperties and stability even when it does not include cadmium and thuswhen it is prepared in a composite form, the quantum dot of anembodiment may provide relatively high absorption (e.g., a ratio of theabsorbance intensity at 450 nm with respect to the absorbance intensityat 350 nm).

Accordingly, a quantum dot of an embodiment does not include cadmium.The quantum dot includes a semiconductor nanocrystal core includingindium (In) and phosphorous (P), a first semiconductor nanocrystal shelldisposed on the semiconductor nanocrystal core and including zinc andselenium, and a second semiconductor nanocrystal shell disposed on thefirst semiconductor nanocrystal shell and including zinc and sulfur. Inan embodiment, the quantum dot may have a core-multi-layered shellstructure. For example, the quantum dot may include a core including anindium phosphide (e.g., InP or InZnP), a first shell directly on thecore and including ZnSe, and a second shell directly on the first shell,having a different composition from the first shell, and including ZnS.In an embodiment, the quantum dot does not include an alkane monothiolcompound on a surface thereof.

In a quantum dot of an embodiment, a molar ratio of sulfur with respectto selenium may be less than or equal to about 2.5:1. In a quantum dotof an embodiment (e.g., emitting green or red light), a molar ratio ofsulfur with respect to selenium may be less than or equal to about2.4:1, less than or equal to about 2.3:1, less than or equal to about2.2:1, less than or equal to about 2.1:1, less than or equal to about2.0:1, less than or equal to about 1.9:1, less than or equal to about1.8:1, less than or equal to about 1.7:1, less than or equal to about1.6:1, less than or equal to about 1.5:1, less than or equal to about1.4:1, less than or equal to about 1.3:1, less than or equal to about1.2:1, less than or equal to about 1.1:1, less than or equal to about1:1, less than or equal to about 0.9:1, or less than or equal to about0.8:1, less than or equal to about 0.7:1, or less than or equal to about0.6:1. In a quantum dot of an embodiment, a molar ratio of sulfur withrespect to selenium may be greater than or equal to about 0.05:1,greater than or equal to about 0.07:1, greater than or equal to about0.1:1, greater than or equal to about 0.2:1, greater than or equal toabout 0.3:1, greater than or equal to about 0.4:1, or greater than orequal to about 0.5:1.

In an embodiment, the quantum dot may emit green light and may have amolar ratio of sulfur with respect to selenium that is greater than orequal to about 0.05:1, greater than or equal to about 0.07:1, greaterthan or equal to about 0.1:1, greater than or equal to about 0.2:1 (forexample, greater than or equal to about 0.3:1) and less than or equal toabout 1.5:1 (for example, less than or equal to about 1.4:1, less thanor equal to about 1.3:1, less than or equal to about 1.2:1, less than orequal to about 1.1:1, less than or equal to about 1:1, less than orequal to about 0.9:1, less than or equal to about 0.8:1, less than orequal to about 0.7:1, or less than or equal to about 0.6:1).

In an embodiment, the quantum dot may emit red light and may have amolar ratio of sulfur with respect to selenium that is greater than orequal to about 0.1:1, greater than or equal to about 0.2:1, greater thanor equal to about 0.3:1 (or greater than or equal to about 0.4:1) andless than or equal to about 2:1 (for example, less than or equal toabout 1.9:1, less than or equal to about 1.8:1, less than or equal toabout 1.7:1, less than or equal to about 1.6:1, less than or equal toabout 1.5:1, less than or equal to about 1.4:1, or less than or equal toabout 1.3:1).

In an embodiment of a quantum dot (emitting green or red light), a moleratio of zinc with respect to indium may be less than or equal to about50:1, less than or equal to about 49:1, less than or equal to about48:1, less than or equal to about 47:1, or less than or equal to about46:1, less than or equal to about 45:1, for example, less than or equalto about 44:1, less than or equal to about 40:1, less than or equal toabout 35:1, less than or equal to about 30:1, less than or equal toabout 25:1, less than or equal to about 20:1, less than or equal toabout 15:1, or less than or equal to about 10:1.

In an embodiment of a quantum dot (emitting green or red light), a moleratio of zinc with respect to indium may be greater than or equal toabout 3:1, greater than or equal to about 4:1, greater than or equal toabout 5:1, greater than or equal to about 6:1, greater than or equal toabout 7:1, greater than or equal to about 8:1, greater than or equal toabout 9:1, greater than or equal to about 10:1, greater than or equal toabout 15:1, greater than or equal to about 20:1, greater than or equalto about 25:1, greater than or equal to about 30:1, greater than orequal to about 35:1, greater than or equal to about 40:1, or greaterthan or equal to about 43:1.

The aforementioned range of the molar ratio may contribute to anincreased level of a blue light absorption rate of the quantum dotemitting green or red light.

In an embodiment, the quantum dot has a maximum photoluminescent peak ina range of about 500 nm to about 550 nm and the molar ratio of thesulfur with respect to the selenium may be greater than or equal toabout 0.1 and less than or equal to about 1 and/or a molar ratio of zincwith respect to indium may be less than or equal to about 48:1, lessthan or equal to about 47:1, less than or equal to about 46:1, less thanor equal to about 45:1, less than or equal to about 44:1 (or less thanor equal to about 35:1) and/or greater than or equal to about 5 (orgreater than or equal to about 6:1, greater than or equal to about 7:1,greater than or equal to about 8:1, greater than or equal to about 9:1,greater than or equal to about 10:1, greater than or equal to about20:1, greater than or equal to about 30:1, greater than or equal toabout 35, greater than or equal to about 40, or greater than or equal toabout 44).

In an embodiment, the quantum dot has a maximum photoluminescent peak ina range of about 600 nm to about 650 nm and the molar ratio of thesulfur with respect to the selenium may be greater than or equal toabout 0.2:1 and less than or equal to about 2:1 and/or a molar ratio ofzinc with respect to indium may be less than or equal to about 30:1,less than or equal to about 28:1, less than or equal to about 25:1, lessthan or equal to about 20:1 and/or greater than or equal to about 3,greater than or equal to about 4:1, greater than or equal to about 5:1,greater than or equal to about 6:1, greater than or equal to about 7:1,greater than or equal to about 8:1, or greater than or equal to about9:1.

The first semiconductor nanocrystal shell may include ZnSe. The firstsemiconductor nanocrystal shell may not include sulfur (S), e.g., may befree of S or have no S added. For example, the first semiconductornanocrystal shell may not include, e.g., may be free of, ZnSeS. Thefirst semiconductor nanocrystal shell may be disposed directly on thesemiconductor nanocrystal core. The first semiconductor nanocrystalshell may have a thickness of greater than or equal to about 3monolayers (ML), for example, greater than or equal to about 3.5 ML,greater than or equal to about 3.6 ML, greater than or equal to about3.7 ML, greater than or equal to about 3.8 ML, greater than or equal toabout 3.9 ML, or greater than or equal to about 4 ML. The firstsemiconductor nanocrystal shell may have a thickness of less than orequal to about 9 ML, less than or equal to about 8 ML, less than orequal to about 7 ML, less than or equal to about for example, 6 ML, orless than or equal to about 5 ML. In an embodiment, the firstsemiconductor nanocrystal shell may have a thickness of greater than orequal to about 0.9 nm, greater than or equal to about 1 nm, greater thanor equal to about 1.1 nm, greater than or equal to about 1.2 nm, greaterthan or equal to about 1.5 nm, greater than or equal to about 1.8 nm andless than or equal to about 3 nm, less than or equal to about 2.7 nm,less than or equal to about 2.5 nm, less than or equal to about 2.2 nm,less than or equal to about 1.4 nm, less than or equal to about 1.3 nm,or less than or equal to about 1.25 nm.

The second semiconductor nanocrystal shell may include ZnS. The secondsemiconductor nanocrystal shell may not include selenium. The secondsemiconductor nanocrystal shell may be disposed directly on the firstsemiconductor nanocrystal shell. The second semiconductor nanocrystalshell may be an outermost layer of the quantum dot. A thickness of thesecond semiconductor nanocrystal shell may be less than 0.7 nm, forexample, less than or equal to about 0.65 nm, less than or equal toabout 0.64 nm, less than or equal to about 0.63 nm, less than or equalto about 0.62 nm, less than or equal to about 0.61 nm, or less than orequal to about 0.6 nm. A thickness of the second semiconductornanocrystal shell may be greater than or equal to about 0.15 nm, greaterthan or equal to about 0.16 nm, greater than or equal to about 0.17 nm,greater than or equal to about 0.18 nm, greater than or equal to about0.19 nm, greater than or equal to about 0.2 nm, greater than or equal toabout 0.21 nm, greater than or equal to about 0.22 nm, greater than orequal to about 0.23 nm, greater than or equal to about 0.24 nm, greaterthan or equal to about 0.25 nm, greater than or equal to about 0.26 nm,or greater than or equal to about 0.27 nm.

In an embodiment, the quantum dot emits green light and a thickness ofthe second semiconductor nanocrystal shell may be greater than or equalto about 0.15 nm, greater than or equal to about 0.16 nm, greater thanor equal to about 0.17 nm, greater than or equal to about 0.18 nm,greater than or equal to about 0.19 nm, or greater than or equal toabout 0.2 nm and less than or equal to about 0.55 nm, less than or equalto about 0.5 nm, less than or equal to about 0.45 nm, or less than orequal to about 0.4 nm.

In an embodiment, the quantum dot emits red light and a thickness of thesecond semiconductor nanocrystal shell may be greater than or equal toabout 0.2 nm, or greater than or equal to about 0.25 nm and less than orequal to about 0.69 nm, less than or equal to about 0.6 nm, less than orequal to about 0.55 nm, or less than or equal to about 0.5 nm.

The present inventors have found that the adoption of the aforementionedshell(s) may makes it possible for the quantum dot of an embodiment toprovide a quantum dot-polymer composite having enhanced excitation lightabsorbance and increased luminous efficiency. For example, in thequantum dot of an embodiment, the thickness of the first semiconductornanocrystal shell (e.g., based on the zinc selenide) within theaforementioned range may have a favorable effect on the increase of theluminous efficiency of the quantum dot. The thickness of the secondsemiconductor nanocrystal shell (e.g., based on the zinc sulfide) withinthe aforementioned range can make it possible, for example, for aquantum dot-polymer composite film including the quantum dot to maintainan excitation light (e.g., a blue light) absorbance at an enhanced,e.g., improved, level without adversely affecting the luminousefficiency thereof.

The quantum dots of an embodiment may include the shell of theaforementioned structure and composition and may exhibit a high level ofchemical stability. As a result, even when the quantum dots of anembodiment undergo a preparation process for a composition includingthem (that involves many contacts with various chemicals such as anorganic polymer, an organic solvent, and various additives) or aproduction process for a composite (or a pattern thereof) using thecomposition, the resulting composition or the resulting composite mayshow an increased luminous properties.

Accordingly, a quantum dot of an embodiment may have a quantumefficiency of greater than or equal to about 65%, for example, greaterthan or equal to about 66%, or greater than or equal to about 67%,greater than or equal to about 68%, greater than or equal to about 69%,or greater than or equal to about 70%. A quantum dot of an embodimentmay have a ratio of absorbance (intensity) at 450 nm with respect toabsorbance at 350 nm that is greater than or equal to about 0.08:1 in aUV-Vis absorption spectrum.

For example, the quantum dot of an embodiment may emit green light and aratio of absorbance (intensity) at 450 nm with respect to absorbance at350 nm may be greater than or equal to about 0.085:1, greater than orequal to about 0.09:1, or greater than or equal to about 0.1:1. In anembodiment, the quantum dot may emit red light and a ratio of absorbance(intensity) at 450 nm with respect to absorbance at 350 nm may begreater than or equal to about 0.11:1, greater than or equal to about0.12:1, or greater than or equal to about 0.13:1. A center wavelength ofthe green light may be in a range of about 500 nm to about 550 nm, and acenter wavelength of the red light may be in a range of about 600 toabout 650 nm.

The light absorbance at about 350 nm for the quantum dot may reflectabsorption of the first semiconductor nanocrystal shell (e.g., ZnSe) andthe second semiconductor nanocrystal shell (e.g., ZnS) for example,which may depend on a size thereof. The light absorbance at about 450 nmmay represent absorption of blue light, e.g., from a blue light source,that is provided with a device including a quantum dot based colorfilter. In the UV-Vis absorption spectrum of the quantum dot, a ratio oflight absorbance at 450 nm with respect to light absorbance at about 350nm may represent a blue light source absorption ability of the quantumdot depending on a shell volume of the quantum dot of an embodiment. Incase of the quantum dot having the aforementioned shell composition, asthe ratio of light absorbance at 450 nm with respect to light absorbanceat about 350 nm increases, a film including the quantum dot may exhibita high level of blue light absorbance.

In an embodiment, the quantum dot-polymer composite may have a 450 nmwavelength blue light absorption rate of greater than or equal to about89%, for example, greater than or equal to about 90%, greater than orequal to about 91%, greater than or equal to about 92%, or greater thanor equal to about 93% when it is in the form of a film with a thicknessof about 6 um and an amount of the quantum dots is less than or equal toabout 45%, based on a total weight of the composite.

In an embodiment, the semiconductor nanocrystal core may further includezinc. The semiconductor nanocrystal core may include InP or InZnP. Thesize of the core may be selected appropriately in light of aphotoluminescence wavelength thereof. For example, the size of the coremay be greater than or equal to about 1 nm, greater than or equal toabout 1.5 nm, greater than or equal to about 2 nm. For example, the sizeof the core may be less than or equal to about 5 nm, less than or equalto about 4 nm, or less than or equal to about 3 nm.

When a maximum luminous peak wavelength of the quantum dot is present ina range of about 500 nm to about 550 nm, a size of the semiconductornanocrystal core may be greater than or equal to about 1 nm (forexample, greater than or equal to about 2 nm) and less than or equal toabout 2.7 nm (for example, less than or equal to about 2.5 nm). When amaximum luminous peak wavelength of the quantum dot is present in arange of about 600 nm to about 650 nm, a size of the semiconductornanocrystal core may be greater than or equal to about 2 nm (forexample, greater than or equal to about 3 nm) and less than or equal toabout 5 nm (for example, less than or equal to about 4 nm).

As used herein, a term regarding a dimension (for example, about aquantum dot related dimension such as a size) may also refer to anaverage dimension (e.g., an average size).

A quantum dot-based display device may exhibit improved color purity,luminance, and the like. For example, a liquid crystal display(hereinafter, LCD) realizes colors by polarized light passing anabsorption type color filter after passing a liquid crystal. LCDs have adrawback of a narrow viewing angle and low light transmittance due tothe absorption type color filter. A quantum dot may emit light havingtheoretical quantum efficiency or quantum yield (QY) of about 100% andhigh color purity (e.g., less than or equal to about 40 nm of a fullwidth at half maximum (FWHM)) and thus achieve increased luminousefficiency and improved color reproducibility. The absorption type colorfilter may be replaced with a photoluminescent type color filterincluding the quantum dot to realize a wider viewing angle and improvedluminance.

The quantum dot may be dispersed in a host matrix (e.g., including apolymer, an inorganic material, or a combination thereof) to form acomposite and thus be applied it to a device. The quantum dot accordingto an embodiment has improved optical properties and process stability,and accordingly, when included in a display device as a quantumdot-polymer composite or a patterned form including a quantumdot-polymer composite, improved luminance, a wide viewing angle, andimproved color reproducibility may be realized. However, the weight ofthe quantum dot included in the composite may be limited for variousreasons regarding a production process. Thus, developing a quantum dotexhibiting enhanced blue light absorption and increased brightness atthe same time and having thermal stability is desired.

As explained above, the quantum dot of an embodiment may include ashell, e.g., coating, and the aforementioned structure and composition,a single quantum dot may have a relatively reduced weight and thus thenumber of the quantum dots included in a given weight may increase, andone or more qualities of the quantum dot may be improved. In addition,the quantum dot of an embodiment may show an improved stability (e.g.,thermal stability) and enhanced optical properties (e.g., quantumefficiency and blue light absorption rate). Accordingly, the quantumdots may be used in a photoluminescent type color filter.

In case of emitting a red light, the quantum dot of an embodiment mayhave a molar ratio of the indium with respect to (a total moles of) thesulfur and the selenium (In/Se+S, hereinafter, also referred to as amolar ratio of indium to sulfur and selenium) of greater than or equalto about 0.09:1, greater than or equal to about 0.1:1, greater than orequal to about 0.11:1, greater than or equal to about 0.12:1, greaterthan or equal to about 0.13:1, greater than or equal to about 0.14:1,greater than or equal to about 0.15:1, greater than or equal to about0.16:1, greater than or equal to about 0.17:1, greater than or equal toabout 0.18:1, greater than or equal to about 0.19:1, or greater than orequal to about 0.20:1. The quantum dot of an embodiment emitting a redlight may have a molar ratio of indium to sulfur and selenium that isless than or equal to about 0.26:1, less than or equal to about 0.25:1,or less than or equal to about 0.22:1.

In an embodiment, the quantum dot may include an InZnP core, emitting agreen light, and may have a molar ratio of indium to sulfur and seleniumthat is greater than or equal to about 0.04:1 or greater than or equalto about 0.05:1 and less than or equal to about 0.18:1 or less than orequal to about 0.16:1.

In the UV-Vis absorption spectrum of the quantum dot, the firstabsorption peak wavelength may be greater than or equal to about 450 nmand less than or equal to about the photoluminescent peak wavelength ofthe quantum dot. For example, in case of the green light emittingquantum dot, the first absorption peak wavelength may be for example,greater than or equal to about 480 nm, greater than or equal to about485 nm, greater than or equal to about 490 nm, or greater than or equalto about 495 nm and less than or equal to about 520 nm, less than orequal to about 515 nm, less than or equal to about 510 nm, or less thanor equal to about 505 nm. In an embodiment, in case of the red lightemitting quantum dot, the first absorption peak wavelength may be forexample, greater than or equal to about 580 nm, greater than or equal toabout 590 nm, greater than or equal to about 595 nm and less than orequal to about 620 nm, less than or equal to about 610 nm, or less thanor equal to about 600 nm.

When it emits a green or red light, a size (or an average size,hereinafter referred to as a size) of the quantum dot may be greaterthan or equal to about 1 nm, greater than or equal to about 2 nm,greater than or equal to about 3 nm, greater than or equal to about 4nm, or greater than or equal to about 5 nm. When it emits a green or redlight, a size of the quantum dot may be less than or equal to about 30nm, for example, less than or equal to about 25 nm, less than or equalto about 24 nm, less than or equal to about 23 nm, less than or equal toabout 22 nm, less than or equal to about 21 nm, less than or equal toabout 20 nm, less than or equal to about 19 nm, less than or equal toabout 18 nm, less than or equal to about 17 nm, less than or equal toabout 15 nm, less than or equal to about 14 nm, less than or equal toabout 13 nm, less than or equal to about 12 nm, less than or equal toabout 11 nm, less than or equal to about 10 nm, less than or equal toabout 9 nm, less than or equal to about 8 nm, or less than or equal toabout 7 nm.

The size of the quantum dot may be a particle diameter. The size of thequantum dot may be a particle diameter, or in the case of anon-spherically shaped particle, the size of the quantum dot may becalculated by converting a (e.g., two-dimensional) area of an electronmicroscopic image of the particle into a circle (e.g., an equivalentcircle area).

In an embodiment, the quantum yield of the quantum dot may be greaterthan or equal to about 60%, greater than or equal to about 65%, greaterthan or equal to about 70%, greater than or equal to about 72%, greaterthan or equal to about 75%, or greater than or equal to about 80%. In anembodiment, a full width at half maximum of a maximum luminescent peakof the quantum dot may be less than or equal to about 45 nm, forexample, less than or equal to about 44 nm, less than or equal to about43 nm, less than or equal to about 42 nm, less than or equal to about 41nm, or less than or equal to about 40 nm.

A shape of the quantum dot is not particularly limited, and may forexample be a spherical, polyhedron, pyramid, multipod, or cube shape,nanotube, nanowire, nanofiber, nanosheet, or a combination thereof, butis not limited thereto.

The quantum dot may include the organic ligand, the organic solvent, ora combination thereof, which will be described below, on a surface ofthe quantum dot. The organic ligand, the organic solvent, or acombination thereof may be bound to the surface of the quantum dot.

In an embodiment, a method of producing the aforementioned quantum dotincludes:

obtaining a first mixture including a first shell precursor containingzinc, an organic ligand, and an organic solvent;

optionally heating the first mixture;

injecting a semiconductor nanocrystal core including indium andphosphorous and a selenium containing precursor to the (optionallyheated) first mixture to obtain a second mixture;

heating the second mixture at a first temperature and keeping the sameat the first reaction temperature for at least about 40 minutes, forexample, at least about 50 minutes to obtain a third mixture including aparticle including a first semiconductor nanocrystal shell includingzinc and selenium formed on the semiconductor nanocrystal core;

injecting a sulfur containing precursor (e.g., a stock solutionincluding the sulfur containing precursor) into the third mixture at thefirst reaction temperature and carrying out a reaction to form a secondsemiconductor nanocrystal shell on the first semiconductor nanocrystalshell,

wherein an amount of the selenium containing precursor and an amount ofthe sulfur containing precursor with respect to the core in the secondmixture and the third mixture are controlled respectively (andoptionally controlling a duration of a reaction in each step) in orderfor a resulting quantum dot to satisfy the aforementioned shellcomposition.

The semiconductor nanocrystal core, the selenium containing precursor,or a combination thereof may be injected as a stock solution with noheating.

Details of the quantum dot, the semiconductor nanocrystal core, thefirst semiconductor nanocrystal shell, and the second semiconductornanocrystal shell are the same as set forth above.

The zinc precursor is not particularly limited and may be selectedappropriately. In an embodiment, the zinc precursor may include a Znmetal powder, an alkylated Zn compound (e.g., dimethyl zinc, diethylzinc, or a combination thereof), a Zn alkoxide, a Zn carboxylate (e.g.,zinc acetate), a zinc carbonate, a Zn nitrate, a Zn perchlorate, a Znsulfate, a Zn acetylacetonate, a Zn halide (e.g., zinc chloride, zincbromide, zinc iodide, zinc fluoride, or a combination thereof), a Zncarbonate, a Zn cyanide, a Zn hydroxide, a Zn oxide, a Zn peroxide, or acombination thereof.

Examples of the first shell precursor may include, but are not limitedto dimethyl zinc, diethyl zinc, zinc acetate, zinc acetylacetonate, zinciodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinccyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate, zincsulfate, and the like. The zinc containing precursor may be used aloneor in a combination of two or more compounds.

The organic ligand may include RCOOH, RNH₂, R₂NH, R₃N, RSH, RH₂PO,R₂HPO, R₃PO, RH₂P, R₂HP, R₃P, ROH, RCOOR′, RPO(OH)₂, RHPOOH, R₂POOH(wherein R and R′ are the same or different, and are independently ahydrogen, a C1 to C40 (or C3 to C24) aliphatic hydrocarbon group (e.g.,a alkyl group, a alkenyl group, or a alkynyl group), a C6 to C40aromatic hydrocarbon group (such as a C6 to C20 aryl group), a polymericorganic ligand, or a combination thereof.

The organic ligand may coordinate to, e.g., be bound to, the surface ofthe obtained nanocrystal and help the nanocrystal to be well dispersedin the solution, may affect light emitting and/or electricalcharacteristics of quantum dots.

Examples of the organic ligand may include methane thiol, ethane thiol,propane thiol, butane thiol, pentane thiol, hexane thiol, octane thiol,dodecane thiol, hexadecane thiol, octadecane thiol, or benzyl thiol;methane amine, ethane amine, propane amine, butyl amine, pentyl amine,hexyl amine, octyl amine, dodecyl amine, hexadecyl amine, octadecylamine, dimethyl amine, diethyl amine, dipropyl amine; methanoic acid,ethanoic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoicacid, heptanoic acid, octanoic acid, dodecanoic acid, hexadecanoic acid,octadecanoic acid, oleic acid, or benzoic acid; phosphine such assubstituted or unsubstituted methyl phosphine (e.g., trimethylphosphine, methyldiphenyl phosphine, etc.), substituted or unsubstitutedethyl phosphine (e.g., triethyl phosphine, ethyldiphenyl phosphine,etc.), substituted or unsubstituted propyl phosphine, substituted orunsubstituted butyl phosphine, substituted or unsubstituted pentylphosphine, or substituted or unsubstituted octylphosphine (e.g.,trioctylphosphine (TOP)); phosphine oxide such as substituted orunsubstituted methyl phosphine oxide (e.g., trimethyl phosphine oxide,methyldiphenyl phosphine oxide, etc.), substituted or unsubstitutedethyl phosphine oxide (e.g., triethyl phosphine oxide, ethyldiphenylphosphine oxide, etc.), substituted or unsubstituted propyl phosphineoxide, substituted or unsubstituted butyl phosphine oxide, orsubstituted or unsubstituted octyl phosphine oxide (e.g.,trioctylphosphine oxide (TOPO); diphenyl phosphine, triphenyl phosphine,diphenyl phosphine oxide, or triphenyl phosphine oxide; analkylphosphinic acid for example, a C5 to C20 alkyl phosphinic acid(e.g., hexyl phosphinic acid, octyl phosphinic acid, dodecanylphosphinic acid, tetradecanyl phosphinic acid, hexadecanyl phosphinicacid, octadecanyl phosphinic acid, or the like, an alkylphosphonic acidsuch as a C5 to C20 alkylphosphonic acid; or the like, but are notlimited thereto. The organic ligand may be used alone or as a mixture ofat least two ligand compounds.

The organic solvent may a C6 to C22 primary amine such ashexadecylamine; a C6 to C22 secondary amine such as dioctylamine; a C6to C40 tertiary amine such as trioctylamine; a nitrogen-containingheterocyclic compound such as pyridine; a C6 to C40 aliphatichydrocarbon (e.g., alkane, alkene, alkyne, etc.) such as hexadecane,octadecane, octadecene, or squalane; a C6 to C30 aromatic hydrocarbonsuch as phenyldodecane, phenyltetradecane, or phenyl hexadecane; aphosphine substituted with a C6 to C22 alkyl group such astrioctylphosphine; a phosphine oxide substituted with a C6 to C22 alkylgroup such as trioctylphosphine oxide; a C12 to C22 aromatic ether suchas phenyl ether, or benzyl ether, or a combination thereof. Types andamounts of the organic solvent may be appropriately selected consideringprecursors and organic ligands.

The first mixture may be heated to a predetermined temperature (e.g., ofgreater than or equal to about 100° C., for example, greater than orequal to about 120° C., greater than or equal to about 150° C., greaterthan or equal to about 200° C., greater than or equal to about 250° C.,or greater than or equal to about 270° C.) and less than or equal toabout the first reaction temperature under vacuum, an inert atmosphere,or a combination thereof.

Details of the semiconductor nanocrystal core including indium andphosphorous are the same as above. The core may be commerciallyavailable or may be prepared in any appropriate method. The preparationof the core is not particularly limited and may be performed in anymethod of producing an indium phosphide based core. In an embodiment,the core may be synthesized in a hot injection manner wherein a solutionincluding a metal precursor (e.g., an indium precursor) and optionally aligand is heated at a high temperature (e.g., of greater than or equalto about 200° C.) and then a phosphorous precursor is injected theheated hot solution.

The selenium precursor is not particularly limited and may be desirablyselected. In an embodiment, the selenium precursor includesselenium-trioctyl phosphine (Se-TOP), selenium-tributyl phosphine(Se-TBP), selenium-triphenyl phosphine (Se-TPP),tellurium-tributylphosphine (Te-TBP), or a combination thereof but isnot limited thereto.

The first reaction temperature may be selected appropriately and, forexample, may be greater than or equal to about 280° C., greater than orequal to about 290° C., greater than or equal to about 300° C., greaterthan or equal to about 310° C., or greater than or equal to about 315°C. and less than or equal to about 390° C., less than or equal to about380° C., less than or equal to about 370° C., less than or equal toabout 360° C., less than or equal to about 350° C., less than or equalto about 340° C., or less than or equal to about 330° C.

After or during the heating to the first reaction temperature, aselenium containing precursor may be injected at least one time (e.g.,at least twice, at least third times).

The reaction time (keeping the second mixture at the first reactiontemperature) may be greater than or equal to about 40 minutes, forexample, greater than or equal to about 50 minutes, greater than orequal to about 60 minutes, greater than or equal to about 70 minutes,greater than or equal to about 80 minutes, greater than or equal toabout 90 minutes, and less than or equal to about 4 hours, for example,less than or equal to about 3 hours, less than or equal to about 2hours.

By the reaction at the first reaction temperature for the aforementionedtime period, the first semiconductor nanocrystal shell including thezinc and the selenium and having a thickness of greater than or equal toabout 3 ML may be formed to provide the third mixture.

In this case, in the second mixture, the amount of the seleniumprecursor with respect to the indium may be controlled such that duringthe predetermined reaction time, the first semiconductor nanocrystalshell having the predetermined thickness may be formed. In anembodiment, the amount of the selenium per one mole of indium may begreater than or equal to about 7 moles, greater than or equal to about 8moles, greater than or equal to about 9 moles, or greater than or equalto about 10 moles, but is not limited there to. In an embodiment, theamount of the selenium per one mole of indium may be less than or equalto about 20 moles, less than or equal to about 18 moles, or less than orequal to about 15 moles, but is not limited thereto.

The third mixture may not include the selenium containing precursor.

At the first reaction temperature, a stock solution including a sulfurcontaining precursor is added to the third mixture to form a secondsemiconductor nanocrystal shell on the first semiconductor nanocrystalshell.

In an embodiment, the method does not include lowering a temperature ofthe third mixture down at or below about 100° C., for example, less thanor equal to about 50° C. (e.g., 30° C. or lower, or room temperature).In other words, the method may include maintaining a temperature of areaction mixture including the particle having the first semiconductornanocrystal shell on the core at a temperature of greater than or equalto 100° C., for example, greater than or equal to 50° C., greater thanor equal to 30° C.

Types of the sulfur containing precursor are not particularly limitedand may be selected appropriately. The sulfur containing precursor mayinclude hexane thiol, octane thiol, decane thiol, dodecane thiol,hexadecane thiol, mercapto propyl silane, sulfur-trioctylphosphine(S-TOP), sulfur-tributylphosphine (S-TBP), sulfur-triphenylphosphine(S-TPP), sulfur-trioctylamine (S-TOA), trimethylsilyl sulfide, sulfideammonium, sodium sulfide, or a combination thereof. The sulfurcontaining precursor may be injected at least one times (e.g., at leasttwo times).

The duration for the formation of the second shell may be greater thanor equal to about 5 minutes, greater than or equal to about 10 minutes,greater than or equal to about 15 minutes, greater than or equal toabout 20 minutes, or greater than or equal to about 25 minutes and lessthan or equal to about 1 hour, less than or equal to about 50 minutes,less than or equal to about 45 minutes, or less than or equal to about40 minutes.

In an embodiment, an amount of sulfur with respect to one mole of indiumin the third mixture may be controlled to obtain a desired shellcomposition (for example, such that the thickness thereof is less thanor equal to about 0.7 nm) considering the reactivity of the precursorand the reaction temperature. For example, the amount of sulfur withrespect to one mole of indium in the third mixture may be greater thanor equal to about 2 moles, greater than or equal to about 3 moles,greater than or equal to about 4 moles, greater than or equal to about 5moles, greater than or equal to about 6 moles, greater than or equal toabout 7 moles, greater than or equal to about 8 moles, greater than orequal to about 9 moles, or greater than or equal to about 10 moles. Theamount of sulfur with respect to one mole of indium in the third mixturemay be, less than or equal to about 45 moles, less than or equal toabout 40 moles, less than or equal to about 35 moles, less than or equalto about 30 moles, less than or equal to about 25 moles, less than orequal to about 20 moles, less than or equal to about 19 moles, less thanor equal to about 18 moles, less than or equal to about 16 moles, lessthan or equal to about 15 moles, less than or equal to about 14 moles,less than or equal to about 13 moles, less than or equal to about 12moles, less than or equal to about 11 moles, less than or equal to about10 moles, less than or equal to about 9 moles, less than or equal toabout 8 moles, less than or equal to about 7 moles, less than or equalto about 6 moles, or less than or equal to about 5 moles.

After the reaction, a non-solvent is added into the obtained finalreaction solution, and thereby organic ligand-coordinated quantum dotsmay be separated (e.g., precipitated). The non-solvent may be a polarsolvent that is miscible with the solvent used in the reaction andnanocrystals are not dispersible therein. The non-solvent may beselected depending on the solvent used in the reaction and may be forexample, acetone, ethanol, butanol, isopropanol, ethanediol, water,tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), diethyl ether,formaldehyde, acetaldehyde, a solvent having a similar solubilityparameter to the foregoing solvents, or a combination thereof. Theseparation may be performed through a centrifugation, precipitation,chromatography, or distillation. The separated nanocrystal may be addedto a washing solvent and washed, if desired. The washing solvent is notparticularly limited and may include a solvent having a similarsolubility parameter to that of the ligand and may, for example, includehexane, heptane, octane, chloroform, toluene, benzene, and the like.

The quantum dots may be dispersed in a dispersing solvent. The quantumdots may form an organic solvent dispersion. The organic solventdispersion may be free of water, may be free of a water miscible organicsolvent, or a combination thereof. The dispersing solvent may beselected appropriately. The dispersing solvent may include (or consistsof) the aforementioned organic solvent. The dispersing solvent mayinclude (or consists of) a substituted or unsubstituted C1 to C40aliphatic hydrocarbon, a substituted or unsubstituted C6 to C40 aromatichydrocarbon, or a combination thereof.

In an embodiment, a composition includes: (for example, a plurality of)the aforementioned quantum dot(s); a dispersing agent; and an organicsolvent, a liquid vehicle, or a combination thereof. The dispersingagent may disperse the quantum dots and may include a carboxylic acidgroup containing a binder. The composition may further include apolymerizable (e.g., photopolymerizable) monomer including acarbon-carbon double bond; and optionally an initiator (e.g., aphotoinitiator or a thermal initiator). The composition may bephotosensitive.

In the composition, details for the quantum dots are the same as setforth above. In the composition, the amount of the quantum dot may beselected appropriately in light of the types and amounts of othercomponents in the composition and a final use thereof. In an embodiment,the amount of the quantum dot may be greater than or equal to about 1weight percent (wt %), for example, greater than or equal to about 2 wt%, greater than or equal to about 3 wt %, greater than or equal to about4 wt %, greater than or equal to about 5 wt %, greater than or equal toabout 6 wt %, greater than or equal to about 7 wt %, greater than orequal to about 8 wt %, greater than or equal to about 9 wt %, greaterthan or equal to about 10 wt %, greater than or equal to about 15 wt %,greater than or equal to about 20 wt %, greater than or equal to about25 wt %, greater than or equal to about 30 wt %, greater than or equalto about 35 wt %, or greater than or equal to about 40 wt %, based on atotal solid content of the composition. The amount of the quantum dotmay be less than or equal to about 70 wt %, for example, less than orequal to about 65 wt %, less than or equal to about 60 wt %, less thanor equal to about 55 wt %, or less than or equal to about 50 wt %, basedon a total solid content of the composition. A weight percent of acomponent, based on a total solid content of the composition, mayrepresent the amount of the component in the composite, which will bedescribed below.

The composition of an embodiment may be used for providing a patternincluding a quantum dot-polymer composite. In an embodiment, thecomposition may be a photoresist composition that may be applicable to aphotolithography process. In other embodiments, the composition may bean ink composition that may be applicable to an ink jet process (e.g., aliquid drop discharging method such as an ink jet printing). In anembodiment, the composition may not include a conjugated polymer (exceptfor a cardo binder that will be described below). In an embodiment, thecomposition may include a conjugated (or electrically conductive)polymer. As used herein, the conjugated polymer may be a polymerincluding a conjugated double bond such as a polyphenylene vinylene.

In the composition of an embodiment, a dispersing agent is a compoundcapable of securing, e.g., improving, a dispersibility of the quantumdots. The dispersing agent may be a binder polymer. The binder polymermay include a carboxylic acid group (for example, in repeating units ofthe binder polymer). The binder polymer may be an (electrically)insulative polymer.

In an embodiment, the binder polymer may include:

a copolymer of a monomer combination including a first monomer, a secondmonomer, and optionally a third monomer, the first monomer including acarboxylic acid group and a carbon-carbon double bond, the secondmonomer including a carbon-carbon double bond and a hydrophobic moietyand not including a carboxylic acid group, and the third monomerincluding a carbon-carbon double bond and a hydrophilic moiety and notincluding a carboxylic acid group;

a multi-aromatic ring-containing polymer including a carboxylic acidgroup (—COOH) and including a backbone structure in a main chain (e.g.,a backbone structure incorporated in the main chain), wherein thebackbone structure includes a cyclic group including a quaternary carbonatom and two aromatic rings bound to the quaternary carbon atom (e.g.,also known as a cardo binder);

or a combination thereof.

The copolymer may include a first repeating unit derived from the firstmonomer, a second repeating unit derived from the second monomer, andoptionally a third repeating unit derived from the third monomer.

Examples of the first monomer may include, but are not limited to,acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaricacid, 3-butenoic acid, and other carboxylic acid vinyl ester compounds.The first monomer may include one or more compounds.

Examples of the second monomer may include, but are not limited to:

alkenyl aromatic compounds such as styrene, α-methyl styrene, vinyltoluene, or vinyl benzyl methyl ether;

unsaturated carboxylic acid ester compounds such as methyl acrylate,methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate,butyl methacrylate, benzyl acrylate, benzyl methacrylate, cyclohexylacrylate, cyclohexyl methacrylate, phenyl acrylate, or phenylmethacrylate;

unsaturated carboxylic acid amino alkyl ester compounds such as 2-aminoethyl acrylate, 2-amino ethyl methacrylate, 2-dimethyl amino ethylacrylate, or 2-dimethyl amino ethyl methacrylate;

maleimides such as N-phenylmaleimide, N-benzylmaleimide, orN-alkylmaleimide;

unsaturated carboxylic acid glycidyl ester compounds such as glycidylacrylate or glycidyl methacrylate;

vinyl cyanide compounds such as acrylonitrile or methacrylonitrile; and

unsaturated amide compounds such as acrylamide or methacrylamide,

but are not limited thereto.

As the second monomer, one or more compounds may be used.

If present, examples of the third monomer may include 2-hydroxy ethylacrylate, 2-hydroxy ethyl methacrylate, hydroxy propyl acrylate, hydroxypropyl methacrylate, 2-hydroxy butyl acrylate, and 2-hydroxy butylmethacrylate, but are not limited thereto. The third monomer may includeone or more compounds.

In an embodiment, in the binder polymer, an amount of the firstrepeating unit, the second repeating unit, or a combination thereof maybe greater than or equal to about 5 mole percent (mol %), for example,greater than or equal to about 10 mol %, greater than or equal to about15 mol %, greater than or equal to about 25 mol %, or greater than orequal to about 35 mol %. In the binder polymer, an amount of the firstrepeating unit, the second repeating unit, or a combination thereof maybe less than or equal to about 95 mol %, for example, less than or equalto about 90 mol %, less than or equal to about 89 mol %, less than orequal to about 88 mol %, less than or equal to about 87 mol %, less thanor equal to about 86 mol %, less than or equal to about 85 mol %, lessthan or equal to about 80 mol %, less than or equal to about 70 mol %,less than or equal to about 60 mol %, less than or equal to about 50 mol%, less than or equal to about 40 mol %, less than or equal to about 35mol %, or less than or equal to about 25 mol %.

If present, in the binder polymer, an amount of a third repeating unitderived from the third monomer, when present, may be greater than orequal to about 1 mol %, for example, greater than or equal to about 5mol %, greater than or equal to about 10 mol %, or greater than or equalto about 15 mol %. In the binder polymer, an amount of the thirdrepeating unit, when present, may be less than or equal to about 30 mol%, for example, less than or equal to about 25 mol %, less than or equalto about 20 mol %, less than or equal to about 18 mol %, less than orequal to about 15 mol %, or less than or equal to about 10 mol %.

In an embodiment, the binder polymer may include a multi-aromaticring-containing polymer. The multi-aromatic ring-containing polymer isalso known as a cardo binder, which may be commercially available.

The carboxylic acid group-containing binder may have an acid value ofgreater than or equal to about 50 milligrams of potassium hydroxide pergram (mg KOH/g). For example, the carboxylic acid group-containingbinder may have an acid value of greater than or equal to about 60 mgKOH/g, greater than or equal to about 70 mg KOH/g, greater than or equalto about 80 mg KOH/g, greater than or equal to about 90 mg KOH/g,greater than or equal to about 100 mg KOH/g, greater than or equal toabout 110 mg KOH/g, greater than or equal to about 120 mg KOH/g, greaterthan or equal to about 125 mg KOH/g, or greater than or equal to about130 mg KOH/g, but is not limited thereto. The carboxylic acidgroup-containing binder may have an acid value of less than or equal toabout 250 mg KOH/g, for example, less than or equal to about 240 mgKOH/g, less than or equal to about 230 mg KOH/g, less than or equal toabout 220 mg KOH/g, less than or equal to about 210 mg KOH/g, less thanor equal to about 200 mg KOH/g, less than or equal to about 190 mgKOH/g, less than or equal to about 180 mg KOH/g, or less than or equalto about 160 mg KOH/g, but is not limited thereto.

The binder polymer (e.g., containing the carboxylic acid group, such asthe carboxylic acid group-containing binder) may have a weight (or anumber) average molecular weight of greater than or equal to about 1,000grams per mole (g/mol), for example, greater than or equal to about2,000 g/mol, greater than or equal to about 3,000 g/mol, or greater thanor equal to about 5,000 g/mol. The binder polymer may have a weight (ora number) average molecular weight of less than or equal to about100,000 g/mol, for example, less than or equal to about 50,000 g/mol,less than or equal to about 25,000 g/mol, or less than or equal to about10,000 g/mol.

In the composition, an amount of the dispersing agent (e.g., the binderpolymer) may be greater than or equal to about 0.5 wt %, for example,greater than or equal to about 1 wt %, greater than or equal to about 5wt %, greater than or equal to about 10 wt %, greater than or equal toabout 15 wt %, or greater than or equal to about 20 wt %, based on atotal weight (or a total solid content) of the composition. In anembodiment, an amount of the carboxylic acid group-containing binder mayless than or equal to about 50 wt %, less than or equal to about 40 wt%, less than or equal to about 35 wt %, less than or equal to about 33wt %, or less than or equal to about 30 wt %, based on a total weight(or a total solid content) of the composition. The amount of the binderpolymer may be greater than or equal to about 0.5 wt % and less than orequal to about 55%.

In the composition according to an embodiment, the (photo)polymerizablemonomer including at least one (e.g., at least two, at least three, ormore) carbon-carbon double bond may include a (e.g., photopolymerizable)(meth)acrylate monomer. The (photo)polymerizable monomer may be aprecursor for an insulative polymer. Examples of the(photo)polymerizable monomer may include, but are not limited to, aC1-C10-alkyl (meth)acrylate, ethylene glycol di(meth)acrylate,triethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate,1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate,pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,dipentaerythritol di(meth)acrylate, dipentaerythritol tri(meth)acrylate,dipentaerythritol penta(meth)acrylate, dipentaerythritolhexa(meth)acrylate, bisphenol A epoxy(meth)acrylate, bisphenol Adi(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene glycolmonomethyl ether (meth)acrylate, novolac epoxy (meth)acrylate, propyleneglycol di(meth)acrylate, tris(meth)acryloyloxyethyl phosphate, or acombination thereof.

The amount of the (photo)polymerizable monomer may be greater than orequal to about 0.5 wt %, for example, greater than or equal to about 1wt %, or greater than or equal to about 2 wt % with respect to a totalweight (or a total solid content) of the composition. The amount of thephotopolymerizable monomer may be less than or equal to about 50 wt %,for example, less than or equal to about 40 wt %, less than or equal toabout 30 wt %, less than or equal to about 28 wt %, less than or equalto about 25 wt %, less than or equal to about 23 wt %, less than orequal to about 20 wt %, less than or equal to about 18 wt %, less thanor equal to about 17 wt %, less than or equal to about 16 wt %, or lessthan or equal to about 15 wt % with respect to a total weight (or atotal solid content) of the composition.

The (photo) initiator included in the composition may be for thepolymerization of the (photo)polymerizable monomer. The initiator may bea compound that can generate a radical species under a mild condition(e.g., by light or heat) to promote the initiation of a radical reaction(e.g., a radical polymerization of a monomer). The initiator may be athermal initiator or a photoinitiator. The initiator is not particularlylimited and may be selected appropriately.

Examples of the thermal initiator may include azobisisobutyronitrile(AIBN), benzoyl peroxide (BPO) or the like but are not limited thereto.

The photoinitiator may be a compound that can initiate a radicalpolymerization of the aforementioned photopolymerizable (e.g., acrylbased) monomer, a thiol compound that will be described below, or acombination thereof. The photoinitiator is not particularly limited. Thephotoinitiator may include a triazine compound, an acetophenonecompound, a benzophenone compound, a thioxanthone compound, a benzoincompound, an oxime compound, an aminoketone compound, a phosphine orphosphine oxide compound, a carbazole compound, a diketone compound, asulfonium borate compound, a diazo compound, a diimidazole compound, acarbazole compound, a diketone compound, a sulfonium borate compound, anazo compound (e.g., diazo compound), a biimidazole compound, or acombination thereof.

In the composition of an embodiment, an amount of the initiator may beadjusted in light of the types and the amount of the photopolymerizablemonomer as used. In an embodiment, the amount of the initiator may begreater than or equal to about 0.01 wt % or greater than or equal toabout 1 wt % and less than or equal to about 10 wt %, less than or equalto about 9 wt %, less than or equal to about 8 wt %, less than or equalto about 7 wt %, less than or equal to about 6 wt %, or less than orequal to about 5 wt %, based on a total weight (or a total solidcontent) of the composition, but is not limited thereto.

The (photosensitive) composition may further include a thiol compound(e.g., a monothiol compound or a multi-thiol compound having two orgreater thiol groups), a metal oxide fine particle, or a combinationthereof.

When a plurality of metal oxide fine particles is present in the polymermatrix, the metal oxide fine particles may include TiO₂, SiO₂, BaTiO₃,Ba₂TiO₄, ZnO, or a combination thereof. An amount of the metal oxidefine particle may be less than or equal to about 50 wt %, less than orequal to about 40 wt %, less than or equal to about 30 wt %, less thanor equal to about 25 wt %, less than or equal to about 20 wt %, lessthan or equal to about 15 wt %, less than or equal to about 10 wt %,less than or equal to about 5 wt %, based on a total weight (or a totalsolid content) of the composition. An amount of the metal oxide fineparticle may be greater than or equal to about 1 wt %, greater than orequal to about 5 wt %, greater than or equal to about 10 wt %, based ona total weight (or a total solid content) of the composition.

A particle size of the metal oxide fine particles is not particularlylimited and may be selected appropriately. The particle size of themetal oxide fine particles may be greater than or equal to about 100 nm,greater than or equal to about 150 nm, or greater than or equal to about200 nm and less than or equal to about 1,000 nm, less than or equal toabout 900 nm, or less than or equal to about 800 nm.

The multi-thiol compound may include a compound represented by ChemicalFormula 1:

wherein,

R¹ is hydrogen; a substituted or unsubstituted C1 to C30 linear orbranched alkyl group; a substituted or unsubstituted C6 to C30 arylgroup; a substituted or unsubstituted C3 to C30 heteroaryl group; asubstituted or unsubstituted C3 to C30 cycloalkyl group; a substitutedor unsubstituted C3 to C30 heterocycloalkyl group; a C1 to C10 alkoxygroup; a hydroxy group; —NH₂; a substituted or unsubstituted C1 to C30amine group, wherein —NRR′, wherein R and R′ are independently hydrogenor C1 to C30 linear or branched alkyl group, but simultaneously nothydrogen; an isocyanate group; a halogen; —ROR′, wherein R is asubstituted or unsubstituted C1 to C20 alkylene group and R′ is hydrogenor a C1 to C20 linear or branched alkyl group; an acyl halide, wherein—RC(═O)X, wherein R is a substituted or unsubstituted alkylene group andX is a halogen; —C(═O)OR′, wherein R′ is hydrogen or a C1 to C20 linearor branched alkyl group; —CN; —C(═O)NRR′, wherein R and R′ areindependently hydrogen or a C1 to C20 linear or branched alkyl group;—C(═O)ONRR′, wherein R and R′ are independently hydrogen or a C1 to C20linear or branched alkyl group; or a combination thereof,

L₁ is a carbon atom, a substituted or unsubstituted C1 to C30 alkylenegroup, a substituted or unsubstituted C1 to C30 alkylene group wherein amethylene is replaced by a sulfonyl moiety, a carbonyl moiety, an ethermoiety, a sulfide moiety, a sulfoxide moiety, an ester moiety, an amidemoiety comprising hydrogen or a C1 to C10 alkyl group, or a combinationthereof, a substituted or unsubstituted C3 to C30 cycloalkylene group, asubstituted or unsubstituted C6 to C30 arylene group, a substituted orunsubstituted C3 to C30 heteroarylene group, or a substituted orunsubstituted C3 to C30 heterocycloalkylene group,

Y₁ is a single bond; a substituted or unsubstituted C1 to C30 alkylenegroup; a substituted or unsubstituted C2 to C30 alkenylene group; or asubstituted or unsubstituted C1 to C30 alkylene group or a substitutedor unsubstituted C2 to C30 alkenylene group wherein a methylene isreplaced by a sulfonyl moiety, a carbonyl moiety, an ether moiety, asulfide moiety, a sulfoxide moiety, an ester moiety, an amide moietycomprising hydrogen or a C1 to C10 linear or branched alkyl group, animine moiety comprising hydrogen or a C1 to C10 linear or branched alkylgroup, or a combination thereof,

m is an integer of 1 or greater,

k1 is 0 or an integer of 1 or greater, k2 is an integer of 1 or greater,and

a sum of m and k2 is an integer of 3 or greater,

provided that m does not exceed the valence of Y₁ and a sum of k1 and k2does not exceed the valence of L₁.

The multi-thiol compound may include a dithiol compound, a trithiolcompound, a tetrathiol compound, or a combination thereof. For example,the multi-thiol compound may include glycol di-3-mercaptopropionate(e.g., ethylene glycol di-3-mercaptopropionate), glycoldimercaptoacetate (e.g., ethylene glycol dimercaptoacetate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritoltetrakis(3-mercaptopropionate), pentaerythritoltetrakis(2-mercaptoacetate), 1,6-hexanedithiol, 1,3-propanedithiol,1,2-ethanedithiol, polyethylene glycol dithiol including 1 to 10ethylene glycol repeating units, or a combination thereof.

Based on a total weight (or a total solid content) of the composition,an amount of the thiol compound may be less than or equal to about 50 wt%, less than or equal to about 40 wt %, less than or equal to about 30wt %, less than or equal to about 20 wt %, less than or equal to about10 wt %, less than or equal to about 9 wt %, less than or equal to about8 wt %, less than or equal to about 7 wt %, less than or equal to about6 wt %, or less than or equal to about 5 wt %. The amount of the thiolcompound may be greater than or equal to about 0.1 wt %, for example,greater than or equal to about 0.5 wt %, greater than or equal to about1 wt %, greater than or equal to about 5 wt %, greater than or equal toabout 10 wt %, or greater than or equal to about 15 wt %, based on atotal weight (or a total solid content) of the composition.

The composition may further include an organic solvent, a liquidvehicle, or a combination thereof (hereinafter, simply referred to as“solvent”). The solvent is not particularly limited. Types and amountsof the solvent may be appropriately selected by considering theaforementioned main components (i.e., the quantum dot, the dispersingagent, the photopolymerizable monomer, the photoinitiator, and if used,the thiol compound), and types and amounts of additives which will bedescribed below. The composition may include a solvent in a residualamount except for a desired amount of the solid content (non-volatilecomponents).

The solvent may be appropriately selected by considering the othercomponents (e.g., a binder, a photopolymerizable monomer, aphotoinitiator, and other additives) in the composition, affinity for analkali-developing solution, a boiling point, or the like. Non-limitingexamples of the solvent and the liquid vehicle may include, but are notlimited to: ethyl 3-ethoxy propionate; an ethylene glycol series such asethylene glycol, diethylene glycol, or polyethylene glycol; a glycolether such as ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, diethylene glycol monomethyl ether, ethylene glycoldiethyl ether, or diethylene glycol dimethyl ether; glycol etheracetates such as ethylene glycol monomethyl ether acetate, ethyleneglycol monoethyl ether acetate, diethylene glycol monoethyl etheracetate, or diethylene glycol monobutyl ether acetate; a propyleneglycol series such as propylene glycol; a propylene glycol ether such aspropylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol monopropyl ether, propylene glycol monobutyl ether,propylene glycol dimethyl ether, dipropylene glycol dimethyl ether,propylene glycol diethyl ether, or dipropylene glycol diethyl ether; apropylene glycol ether acetate such as propylene glycol monomethyl etheracetate or dipropylene glycol monoethyl ether acetate; an amide such asN-methylpyrrolidone, dimethyl formamide, or dimethyl acetamide; a ketonesuch as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), orcyclohexanone; a petroleum product such as toluene, xylene, or solventnaphtha; an ester such as ethyl acetate, propyl acetate, butyl acetate,cyclohexyl acetate, or ethyl lactate; an ether such as diethyl ether,dipropyl ether, or dibutyl ether; chloroform, a C1 to C40 aliphatichydrocarbon (e.g., alkane, alkene, or alkyne), a halogen (e.g., chloro)substituted C1 to C40 aliphatic hydrocarbon (e.g., dichloroethane,trichloromethane, or the like), a C6 to C40 aromatic hydrocarbon (e.g.,toluene, xylene, or the like), a halogen (e.g., chloro) substituted C6to C40 aromatic hydrocarbon, or a combination thereof.

The composition may further include various additives such as a lightdiffusing agent, a leveling agent, or a coupling agent, in addition tothe aforementioned components. The amount of the additive is notparticularly limited, and may be selected within an appropriate range,wherein the additive does not cause an adverse effect on the preparationof the composition, the preparation of the quantum dot-polymercomposite, and optionally, the patterning of the composite. Types andexamples of the aforementioned additives may include any suitablecompound having a desired function and are not particularly limited.

If present, the amount of the additives may be, based on a total weightof the composition (or a total solid content of the composition),greater than or equal to about 0.1 wt %, for example, greater than orequal to about 0.5 wt %, greater than or equal to about 1 wt %, greaterthan or equal to about 2 wt %, or greater than or equal to about 5 wt %,but it is not limited thereto. If present, the amount of the additivesmay be less than or equal to about 20 wt %, for example, less than orequal to about 19 wt %, less than or equal to about 18 wt %, less thanor equal to about 17 wt %, less than or equal to about 16 wt %, or lessthan or equal to about 15 wt %, but it is not limited thereto.

The composition according to an embodiment may be prepared by a methodincluding: preparing quantum dot dispersion including the aforementionedquantum dots, the dispersing agent, and the solvent; and mixing thequantum dot dispersion with the initiator; the polymerizable monomer(e.g., acryl-based monomer); optionally the thiol compound; optionallythe metal oxide particulate, and optionally the additives. Eachcomponent may be mixed sequentially or simultaneously, but a mixingorder is not particularly limited.

The composition may provide a quantum dot-polymer composite or a quantumdot pattern via polymerization (e.g., photopolymerization).

In an embodiment, a quantum dot-polymer composite may include a polymermatrix; and the aforementioned quantum dots dispersed in the polymermatrix.

The polymer matrix may include at least one of a dispersing agent (e.g.,a binder polymer including a carboxylic acid group), a polymerizationproduct (e.g., insulating polymer) of a polymerizable monomer includinga carbon-carbon double bond (at least one, for example, at least two, atleast three, at least four, or at least five) optionally apolymerization product of the polymerizable monomer a multiple thiolcompound including at least two thiol groups (e.g., at a terminal end ofthe multiple thiol compound), or a combination thereof, and a metaloxide particulate(s).

In an embodiment, the polymer matrix may include a cross-linked polymerand a dispersing agent (e.g., (carboxyl group-contained) binderpolymer). The polymer matrix may not include a conjugated polymer(except for a cardo binder). The cross-linked polymer may include athiolene resin, a cross-linked poly(meth)acrylate, or a combinationthereof. In an embodiment, the cross-linked polymer may be apolymerization product of the polymerizable monomer and, optionally, themultiple thiol compound.

Details of the quantum dots, the dispersing agent, or the binderpolymer, the polymerizable monomer, and the multiple thiol compound arethe same as described above.

The film of the quantum dot-polymer composite or the quantum dot-polymercomposite pattern that will be described below may have for example athickness, less than or equal to about 30 μm, for example less than orequal to about 25 μm, less than or equal to about 20 μm, less than orequal to about 15 μm, less than or equal to about 10 μm, less than orequal to about 8 μm, less than or equal to about 7 μm and greater thanabout 2 μm, for example, greater than or equal to about 3 μm, greaterthan or equal to about 3.5 μm, greater than or equal to about 4 μm,greater than or equal to about 5 μm, or greater than or equal to about 6μm.

In an embodiment, a patterned film includes a repeating sectionincluding a first section emitting first light, wherein the firstsection includes the quantum dot-polymer composite.

The repeating section may include a second section emitting second lighthaving a different maximum peak wavelength from that of the first light.The second section may include a quantum dot-polymer composite. Thequantum dot-polymer composite of the second section may include a secondquantum dot configured to emit the second light. The second quantum dotmay include the aforementioned quantum dot. The first light or thesecond light may be red light having a maximum photoluminescence peakwavelength which is present between about 600 nm and about 650 nm (e.g.,about 620 nm to about 650 nm) or green light having a maximumphotoluminescence peak wavelength which is present between about 500 nmand about 550 nm (e.g., about 510 nm to about 540 nm). The patternedfilm may further include a third section emitting or passing third light(e.g., blue light) different from the first light and the second light.The third light may have a maximum peak wavelength ranging from 380 nmto 480 nm.

In an embodiment, a display device includes a light source and aphotoluminescence element, and the photoluminescence element includes asubstrate and an emission layer disposed on the substrate, and theemission layer includes a film or patterned film of the quantumdot-polymer composite. The light source is configured to provide thephotoluminescence element with incident light. The incident light mayhave a photoluminescence peak wavelength of greater than or equal toabout 440 nm, for example, greater than or equal to about 450 nm andless than or equal to about 500 nm, for example, less than or equal toabout 480 nm, less than or equal to about 470 nm, or less than or equalto about 460 nm.

In the emission layer (e.g., patterned film of quantum dot-polymercomposite) of the device according to an embodiment, the first sectionmay be a section emitting red light, and the second section may be asection emitting green light, and the light source may be an elementemitting blue light.

An optical element (e.g., a blue light blocking layer or a first opticalfilter which will be described below) for blocking (e.g., reflecting orabsorbing) blue light may be disposed on a front surface (alight-emitting surface) of the first section, the second section, or acombination thereof.

In the display device, the light source may include a plurality of lightemitting units corresponding to the first section and the secondsection, respectively, and the light emitting units may include a firstelectrode and a second electrode facing each other and anelectroluminescence layer disposed between the first electrode and thesecond electrode. The electroluminescence layer may include an organiclight emitting material. For example, each light emitting unit of thelight source may include an electroluminescent device (e.g., an organiclight emitting diode (OLED)) configured to emit light of a predeterminedwavelength (e.g., blue light, green light, or a combination thereof).Structures and materials of the electroluminescent device and theorganic light emitting diode (OLED) may be selected appropriately andare not particularly limited. The light source includes an organic lightemitting diode (OLED) emitting blue light (and optionally, green light).

FIGS. 1 and 2 are schematic cross-sectional views of display devicesaccording to embodiments. Referring to FIGS. 1 and 2 , a light sourceincludes an organic light emitting diode (OLED) emitting blue light. Theorganic light emitting diode OLED may include (at least two, forexample, three or more) pixel electrodes 90 a, 90 b, 90 c formed on asubstrate 100, a pixel defining layer 150 a, 150 b formed between theadjacent pixel electrodes 90 a, 90 b, 90 c, an organic light emittinglayer 140 a, 140 b, 140 c formed on the pixel electrodes 90 a, 90 b, 90c, and a common electrode layer 130 formed on the organic light emittinglayer 140 a, 140 b, 140 c.

A thin film transistor and a substrate may be disposed under the organiclight emitting diode (OLED).

The pixel areas of the OLED may be disposed corresponding to the first,second, and third sections that will be described in detail below,respectively.

A stack structure including a quantum dot-polymer composite (e.g., asection including red quantum dot and a section including green quantumdot) pattern and a substrate may be disposed on the light source. Thesections are configured so that blue light emitted from the light sourceis entered thereinto and red light and green light may be emitted,respectively. Blue light emitted from the light source may pass throughthe third section.

The light (e.g., blue light) emitted from the light source may enter thesecond section 21 and the first section 11 of the pattern 170 to emit(e.g., converted) red light R and green light G, respectively. The bluelight B emitted from the light source passes through or transmits fromthe third section 31. Over the second section emitting red light, thefirst section emitting green light, or a combination thereof, an opticalelement 160 may be disposed. The optical element may be a blue cut layerwhich cuts (e.g., reflects or absorbs) blue light and optionally greenlight, or a first optical filter. The blue cut layer 160 may be disposedon the upper substrate 240. The blue cut layer 160 may be disposedbetween the upper substrate 240 and the quantum dot-polymer compositepattern and over the first section 11 and the second section 21. Detailsof the blue cut layer are the same as set forth for the first opticalfilter 310 below.

The device may be obtained by separately fabricating the stack structureand (e.g., blue light emitting) LED or OLED and then assembling thesame. Alternatively, the device may be obtained by forming a quantumdot-polymer composite pattern directly on the LED or OLED.

The substrate may be a substrate including an insulating material. Thesubstrate may include glass; various polymers such as a polyester (e.g.,polyethylene terephthalate (PET) polyethylene naphthalate (PEN), apolymethacrylate, or a polyacrylate); a polycarbonate; a polysiloxane(e.g., polydimethylsiloxane (PDMS)); an inorganic material such as Al₂O₃or ZnO; or a combination thereof, but is not limited thereto. Athickness of the substrate may be selected appropriately considering asubstrate material but is not particularly limited. The substrate mayhave flexibility. The substrate may have a transmittance of greater thanor equal to about 50%, greater than or equal to about 60%, greater thanor equal to about 70%, greater than or equal to about 80%, or greaterthan or equal to about 90% for light emitted from the quantum dot.

A wire layer including a thin film transistor or the like is formed onthe substrate. The wire layer may further include a gate line, a sustainvoltage line, a gate insulating layer, a data line, a source electrode,a drain electrode, a semiconductor, a protective layer, and the like.The detail structure of the wire layer may be verified according to anembodiment. The gate line and the sustain voltage line are electricallyseparated from each other, and the data line is insulated and crossingthe gate line and the sustain voltage line. The gate electrode, thesource electrode, and the drain electrode form a control terminal, aninput terminal, and an output terminal of the thin film transistor,respectively. The drain electrode is electrically connected to the pixelelectrode that will be described below.

The pixel electrode may function as an anode of the display device. Thepixel electrode may be formed of a transparent conductive material suchas indium tin oxide (ITO) or indium zinc oxide (IZO). The pixelelectrode may be formed of a material having a light-blocking propertysuch as gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium(Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium(Pd), or titanium (Ti). The pixel electrode may have a two-layeredstructure where the transparent conductive material and the materialhaving light-blocking properties are stacked sequentially.

Between two adjacent pixel electrodes, a pixel define layer (PDL)overlapped with a terminal end of the pixel electrode to divide thepixel electrode into a pixel unit. The pixel define layer is aninsulation layer which may electrically block the at least two pixelelectrodes.

The pixel define layer covers a part of the upper surface of the pixelelectrode, and the remaining region of the pixel electrode where is notcovered by the pixel define layer may provide an opening. An organicemission layer that will be described below may be formed on the regiondefined by the opening.

The organic emission layer defines each pixel area by the pixelelectrode and the pixel define layer. In other words, one pixel area maybe defined as an area where is formed with one organic emission unitlayer which is contacted with one pixel electrode divided by the pixeldefine layer.

For example, in the display device according to an embodiment, theorganic emission layer may be defined as a first pixel area, a secondpixel area and a third pixel area, and each pixel area is spaced apartfrom each other leaving a predetermined interval by the pixel definelayer.

In an embodiment, the organic emission layer may emit a third lightbelong to visible light region or belong to UV region. That is, each ofthe first to the third pixel areas of the organic emission layer mayemit a third light. In an embodiment, the third light may be a lighthaving the highest energy in the visible light region, for example, maybe blue light. When all pixel areas of the organic emission layer aredesigned to emit the same light, each pixel area of the organic emissionlayer may be all formed of the same or similar materials or may show thesame or similar properties. Thus it may significantly relieve a processdifficulty of forming the organic emission layer, so the display devicemay be easily applied for the large scale/large area process. However,the organic emission layer according to an embodiment is not necessarilylimited thereto, but the organic emission layer may be designed to emitat least two different lights.

The organic emission layer includes an organic emission unit layer ineach pixel area, and each organic emission unit layer may furtherinclude an auxiliary layer (e.g., hole injection layer (HIL), holetransport layer (HTL), electron transport layer (ETL), etc.) besides theemission layer.

The common electrode may function as a cathode of the display device.The common electrode may be formed of a transparent conductive materialsuch as indium tin oxide (ITO) or indium zinc oxide (IZO). The commonelectrode may be formed on the organic emission layer and may beintegrated therewith.

A planarization layer or a passivation layer may be formed on the commonelectrode. The planarization layer may include a (e.g., transparent)insulating material for ensuring electrical insulation with the commonelectrode.

In an embodiment, the display device may further include a lowersubstrate, a polarizer disposed under the lower substrate, and a liquidcrystal layer disposed between the stack structure and the lowersubstrate, and in the stack structure, the light emission layer may bedisposed to face the liquid crystal layer. The display device mayfurther include a polarizer between the liquid crystal layer and theemission layer. The light source may further include LED and if desired,a light guide panel.

Non-limiting examples of the display device (e.g., a liquid crystaldisplay device) according to an embodiment are illustrated with areference to a drawing. FIG. 3 is a schematic cross sectional viewshowing a liquid crystal display according to an embodiment. The displaydevice of an embodiment includes a liquid crystal panel 200, a polarizer300 disposed under the liquid crystal panel 200, and a backlight unit(BLU) disposed under the polarizer 300.

The liquid crystal panel 200 includes a lower substrate 210, a stackstructure, and a liquid crystal layer 220 disposed between the stackstructure and the lower substrate. The stack structure includes atransparent substrate 240 and a photoluminescent layer 230 including apattern including a quantum dot-polymer composite.

The lower substrate 210 also referred to be an array substrate may be atransparent insulating material substrate. The substrate is the same asdescribed above. A wire plate 211 is provided on an upper surface of thelower substrate 210. The wire plate 211 may include a plurality of gatewires and data wires that define a pixel area, a thin film transistordisposed adjacent to a crossing region of gate wires and data wires, anda pixel electrode for each pixel area, but is not limited thereto.Details of such a wire plate are known and are not particularly limited.

The liquid crystal layer 220 may be disposed on the wire plate 211. Theliquid crystal layer 220 may include an alignment layer 221 on and underthe layer 220 to initially align the liquid crystal material includedtherein. Details (e.g., a liquid crystal material, an alignment layermaterial, a method of forming liquid crystal layer, a thickness ofliquid crystal layer, or the like) of the liquid crystal material andthe alignment layer are known and are not particularly limited.

A lower polarizer 300 is provided under the lower substrate. Materialsand structures of the polarizer 300 are known and are not particularlylimited. A backlight unit (e.g., emitting blue light) may be disposedunder the polarizer 300.

An upper optical element or an upper polarizer 300 may be providedbetween the liquid crystal layer 220 and the transparent substrate 240,but is not limited thereto. For example, the upper polarizer may bedisposed between the liquid crystal layer 220 and the light emissionlayer 230. The polarizer may be any polarizer that used in a liquidcrystal display device. The polarizer may be TAC (triacetyl cellulose)having a thickness of less than or equal to about 200 μm, but is notlimited thereto. In an embodiment, the upper optical element may be acoating that controls a refractive index without a polarizationfunction.

The backlight unit includes a light source 110. The light source mayemit blue light or white light. The light source may include a blue LED,a white LED, a white OLED, or a combination thereof, but is not limitedthereto.

The backlight unit may further include a light guide panel 120. In anembodiment, the backlight unit may be an edge-type lighting. Forexample, the backlight unit may include a reflector, a light guide panelprovided on the reflector and providing a planar light source with theliquid crystal panel 200, at least one optical sheet on the light guidepanel, for example, a diffusion plate, a prism sheet, and the like, or acombination thereof, but is not limited thereto. The backlight unit maynot include a light guide panel. In an embodiment, the backlight unitmay be a direct lighting. For example, the backlight unit may have areflector, and may have a plurality of fluorescent lamps disposed on thereflector at regular intervals, or may have an LED operating substrateon which a plurality of light emitting diodes may be disposed, adiffusion plate thereon, and optionally at least one optical sheet.Details (e.g., each component of a light emitting diode, a fluorescentlamp, light guide panel, various optical sheets, and a reflector) ofsuch a backlight unit are known and are not particularly limited.

A black matrix 241 is provided under the transparent substrate 240 andhas openings and hides a gate line, a data line, and a thin filmtransistor of the wire plate on the lower substrate. For example, theblack matrix 241 may have a lattice shape. The photoluminescent layer230 is provided in the openings of the black matrix 241 and has aquantum dot-polymer composite pattern including a first section (R)configured to emit a first light (e.g., red light), a second section (G)configured to emit a second light (e.g., green light), and a thirdsection (B) configured to emit/transmit, for example blue light. Ifneeded, the photoluminescent layer may further include at least onefourth section. The fourth section may include a quantum dot that emitsdifferent color from light emitted from the first to third sections(e.g., cyan, magenta, and yellow light).

In the light emission layer 230, sections forming a pattern may berepeated corresponding to pixel areas formed on the lower substrate. Atransparent common electrode 231 may be provided on the photoluminescentlayer 230 (e.g., photoluminescent color filter layer).

The third section (B) configured to emit/transmit blue light may be atransparent color filter that does not change a light emitting spectrumof the light source. In this case, blue light emitted from the backlightunit may enter in a polarized state and may be emitted through thepolarizer and the liquid crystal layer as it is. If needed, the thirdsection may include a quantum dot emitting blue light.

If desired, the display device may further include a light blockinglayer (blue cut filter) or a first optical filter layer. The blue lightblocking layer may be disposed between bottom surfaces of the firstsection (R) and the second section (G) and the upper substrate 240 or ona top surface of the upper substrate 240. The blue light blocking layermay include a sheet having openings that correspond to a pixel areashowing a blue color (e.g., third section) and may be formed on portionscorresponding to the first and second sections. The first optical filterlayer may be integrally formed as one body structure at the portionsexcept portions overlapped with the third section, but is not limitedthereto. At least two first optical filter layers may be spaced apartand be disposed on each of the positions overlapped with the first andthe second sections.

In an embodiment, the first optical filter layer may block light havinga portion of a wavelength region in the visible light region andtransmit light having other wavelength regions. For example, the firstoptical filter layer may block blue light and transmit light except bluelight. For example, the first optical filter layer may transmit greenlight, red light, and/or or yellow light that is mixed light thereof.

In an embodiment, the first optical filter layer may substantially blockblue light having a wavelength of less than or equal to about 500 nm andmay transmit light in another visible light wavelength region of greaterthan about 500 nm and less than or equal to about 700 nm.

In an embodiment, the first optical filter layer may have lighttransmittance of greater than or equal to about 70%, greater than orequal to about 80%, greater than or equal to about 90%, or even about100% with respect to the other visible light of greater than about 500nm and less than or equal to about 700 nm.

The first optical filter layer may include a polymer thin film includinga dye, a pigment, or a combination thereof that absorbs light having awavelength to be blocked. The first optical filter layer may block atleast 80%, or at least 90%, even at least 95% of blue light having awavelength of less than or equal to about 480 nm and it may have lighttransmittance of greater than or equal to about 70%, greater than orequal to about 80%, greater than or equal to about 90%, or even about100% with respect to other visible light of greater than about 500 nmand less than or equal to about 700 nm.

The first optical filter layer may block (e.g., absorb) andsubstantially block blue light having a wavelength of less than or equalto about 500 nm and for example may selectively transmit green light orred light. In this case, at least two first optical filter layers may bespaced apart and disposed on each of the portions overlapped with thefirst and second sections, respectively. For example, a first opticalfilter layer selectively transmitting red light may be disposed on theportion overlapped with the section emitting red light and the firstoptical filter layer selectively transmitting green light may bedisposed on the portion overlapped with the section emitting greenlight, respectively. For example, the first optical filter layer mayinclude at least one of a first region and a second region wherein thefirst region blocks (e.g., absorb) blue light and red light andtransmits light having a wavelength of a predetermined range (e.g.,greater than or equal to about 500 nm, greater than or equal to about510 nm, or greater than or equal to about 515 nm and less than or equalto about 550 nm, less than or equal to about 545 nm, less than or equalto about 540 nm, less than or equal to about 535 nm, less than or equalto about 530 nm, less than or equal to about 525 nm, or less than orequal to about 520 nm) and the second region blocks (e.g., absorb) bluelight and green light and transmits light having a wavelength of apredetermined range (e.g., greater than or equal to about 600 nm,greater than or equal to about 610 nm, or greater than or equal to about615 nm and less than or equal to about 650 nm, less than or equal toabout 645 nm, less than or equal to about 640 nm, less than or equal toabout 635 nm, less than or equal to about 630 nm, less than or equal toabout 625 nm, or less than or equal to about 620 nm). The first regionmay be disposed at a place overlapped with the section emitting greenlight and the second region may be disposed at a place overlapped withthe section emitting red light. The first region and the second regionmay be optically isolated. The first optical filter (layer) maycontribute to improving color purity of a display device.

The first optical filter layer may be a reflective filter including aplurality of layers (e.g., inorganic material layers) with differentrefractive index. For example two layers having different refractiveindex may be alternately stacked with each other, or for example a layerhaving a high refractive index and a layer having a low refractive indexmay be alternately stacked with each other.

As refractive index different between the layer having a high refractiveindex and the layer having a low refractive index is higher, the firstoptical filter layer having higher wavelength selectivity may beprovided. A thickness and the number of the stacked layer having a highrefractive index and the layer having a low refractive index may bedetermined according to a refractive index of each layer and a reflectedwavelength, for example, each layer having a high refractive index mayhave a thickness of about 3 nm to about 300 nm, and each layer having alow refractive index may have a thickness of about 3 nm to about 300 nm.

A total thickness of the first optical filter layer may be, for example,from about 3 nm to about 10,000 nm, about 300 nm to about 10,000 nm, orabout 1,000 nm to about 10,000 nm. The high refractive index layers mayhave the same thickness, the same material, or a combination thereof asone another or a different thickness, a different material, or acombination thereof from each other. The low refractive index layers mayhave the same thickness, the same material, or a combination thereof asone another or a different thickness, a different material, or acombination thereof from each other.

The display device may further include a second optical filter layer 311(e.g., a red/green or yellow light recycling layer) disposed between thelight emission layer and the liquid crystal layer (e.g., between a lightemission layer and an upper polarizer) and transmitting at least a partof the third light and reflecting at least a part of the first light andthe second light. The second optical filter layer may reflect light in awavelength region of greater than about 500 nm. The first light may bered light, the second light may be green light, and the third light maybe blue light.

In the display device according to an embodiment, the second opticalfilter layer may be formed as an integrated single layer having anapproximately planar surface.

In an embodiment, the second optical filter layer may include amonolayer having a low refractive index, for example, it may be atransparent thin film having a refractive index of less than or equal toabout 1.4, less than or equal to about 1.3, or less than or equal toabout 1.2.

The second optical filter layer having a low refractive index may be,for example, a porous silicon oxide, a porous organic material, a porousorganic/inorganic composite, or a combination thereof.

In an embodiment, the second optical filter layer may include aplurality of layers having different refractive indexes, for example, itmay be formed by alternatively stacking two layers having differentrefractive indexes, or for example, it may be formed by alternativelystacking material having a high refractive index and material having alow refractive index.

The layer having a high refractive index in the second optical filterlayer may include, for example, at least one of hafnium oxide, tantalumoxide, titanium oxide, zirconium oxide, magnesium oxide, cesium oxide,lanthanum oxide, indium oxide, niobium oxide, aluminum oxide, andsilicon nitride, but according to embodiments, it may include a varietyof materials having a higher refractive index than the layer having alow refractive index.

The layer having a low refractive index in the second optical filterlayer may include, for example, a silicon oxide, but according toembodiments, it may include a variety of materials having a lowerrefractive index than the layer having a high refractive index.

As the refractive index difference between the layer having a highrefractive index and the layer having a low refractive index is thehigher, the second optical filter layer may have the higher wavelengthselectivity.

In the second optical filter layer, each thickness of the layer having ahigh refractive index and the layer having a low refractive index andthe stacked number thereof may be determined depending upon a refractiveindex of each layer and the reflected wavelength, for example, eachlayer having a high refractive index in the second optical filter layermay have a thickness of about 3 nm to about 300 nm, and each layerhaving a low refractive index in the second optical filter layer mayhave a thickness of about 3 nm to about 300 nm. A total thickness of thesecond optical filter layer may be, for example, from about 3 nm toabout 10,000 nm, about 300 nm to about 10,000 nm, or about 1,000 nm toabout 10,000 nm. Each of the layer having a high refractive index andthe layer having a low refractive index in the second optical filterlayer may have the same thickness and materials or different thicknessand materials from each other.

The second optical filter layer may reflect at least one part of thefirst light (R) and the second light (G) and transmits at least one part(e.g., whole part) of the third light (B). For example, the secondoptical filter layer may transmit only the third light (B) in a bluelight wavelength region of less than or equal to about 500 nm and lightin a wavelength region of greater than about 500 nm, that is, greenlight (G), yellow light, red light (R), and the like may be not passedthrough the second optical filter layer and reflected. Thus thereflected green light and red light may pass through the first and thesecond sections to be emitted to the outside of the display device 10.

The second optical filter layer may reflect a wavelength region ofgreater than about 500 nm in greater than or equal to about 70%, greaterthan or equal to about 80%, or greater than or equal to about 90%, oreven about 100%.

Meanwhile, the second optical filter layer may have a transmittance to awavelength region of less than or equal to about 500 nm of, for example,greater than or equal to about 90%, greater than or equal to about 92%,greater than or equal to about 94%, greater than or equal to about 96%,greater than or equal to about 98%, greater than or equal to about 99%,or even about 100%.

In an embodiment, the stack structure may be produced by a method usingthe photoresist composition. The method may include

forming a film of the composition on a substrate;

exposing a selected region of the film to light (e.g., a wavelength ofless than or equal to about 400 nm); and

developing the exposed film with an alkali developing solution to obtaina pattern including the quantum dot-polymer composite.

The substrate and the composition have the same specification asdescribed above. Non-limiting methods of forming the pattern areillustrated, referring to FIG. 4 .

The composition is coated to have a predetermined thickness on asubstrate in an appropriate method of spin coating, slit coating, andthe like (S1). The formed film may be, optionally, pre-baked (PRB) (S2).The pre-baking may be performed by selecting an appropriate conditionfrom known conditions of a temperature, time, an atmosphere, and thelike.

The formed (or optionally pre-baked) film is exposed to light having apredetermined wavelength under a mask having a predetermined pattern(S3). A wavelength and intensity of the light may be selectedconsidering types and amounts of the photoinitiator, types and amountsof the quantum dots, and the like.

The exposed film is treated with an alkali developing solution (e.g.,dipping or spraying) to dissolve an unexposed region and obtain adesired pattern (S4). The obtained pattern may be, optionally,post-baked (FOB) to improve crack resistance and solvent resistance ofthe pattern, for example, at about 150° C. to about 230° C. for apredetermined time (e.g., greater than or equal to about 10 minutes orgreater than or equal to about 20 minutes) (S5).

In an embodiment where the quantum dot-polymer composite pattern has aplurality of repeating sections, a quantum dot-polymer composite havinga desired pattern may be obtained by preparing a plurality ofcompositions including a quantum dot having desired photoluminescenceproperties (a photoluminescence peak wavelength and the like) to formeach repeating section (e.g., a red light emitting quantum dot, a greenquantum dot, or optionally, a blue quantum dot) and an appropriatenumber of times (e.g., twice or more or three times or more) repeating aformation of the above pattern about each composition (S6). For example,the quantum dot-polymer composite may have, e.g., be provided in, apattern including at least two repeating color sections (e.g., RGBsections). The quantum dot-polymer composite pattern may be used as aphotoluminescence-type color filter in a display device.

In an embodiment, the stack structure may be produced using an inkcomposition. The method may include depositing the same (e.g., toprovide a desirable pattern) on the desirable substrate using anappropriate system (e.g., droplet discharging device such as inkjet ornozzle printing device) and heating the same to remove a solvent and toperform a polymerization. The method may provide a highly precisequantum dot-polymer composite film or pattern in a simple and rapid way.

An embodiment provides an electronic device including the quantum dot.The device may include a light emitting diode (LED), an organic lightemitting diode (OLED), a sensor, a solar cell, an imaging sensor, or aliquid crystal display (LCD), but is not limited thereto

Hereinafter, the embodiments are illustrated in more detail withreference to examples. However, they are exemplary embodiments of thepresent invention, and the present invention is not limited thereto.

EXAMPLES

Analysis Methods

1. Ultraviolet (UV)-Visible (Vis) Absorption Analysis

An Agilent Cary5000 spectrometer is used to perform a UV spectroscopyanalysis and UV-Visible absorption spectrum is obtained.

2. Photoluminescence Analysis

Photoluminescence Analysis is done using Hitachi F-7000 spectrometer anda photoluminescence spectrum is obtained.

3. ICP Analysis

An inductively coupled plasma-atomic emission spectroscopy (ICP-AES)analysis is performed using Shimadzu ICPS-8100.

4. Brightness and Luminous Efficiency of Quantum Dot Polymer Composite

Light dose of blue excitation light (B) is measured by using anintegrating sphere. Then, a QD polymer composite is placed in theintegrating sphere and is irradiated with the blue excitation light tomeasure a green (or red) light dose (A) emitted from the composite and ablue light dose (B′) passing the composite.

The blue light absorption and the quantum efficiency are obtainedaccording to the following formulae:Blue light absorption rate=(B-B′)/B×100%Quantum efficiency=A/B×100%

B: Light dose of blue excitation light

A: Light dose of green (or red) light emitted from composite byirradiating blue excitation light

B′: Light dose of blue excitation light emitted from composite

Production of InP and InZnP cores

Reference Example 1: InP cores are prepared in the following manner.

Indium acetate and palmitic acid are dissolved in 1-octadecene in a 200milliliters (mL) reaction flask, subjected to a vacuum state at 120° C.for one hour. A molar ratio of indium to palmitic acid is 1:3. Theatmosphere in the flask is exchanged with N₂. After the reaction flaskis heated to 280° C., a mixed solution of tris(trimethylsilyl)phosphine(TMS₃P) and trioctylphosphine (TOP) is quickly injected, and thereaction proceeds for a predetermined time (e.g., for about 20 minutes).The reaction mixture then is rapidly cooled to room temperature andacetone is added thereto to produce nanocrystals, which are thenseparated by centrifugation and dispersed in toluene to obtain a toluenedispersion of the InP core nanocrystals. The amount of the TMS₃P isabout 0.75 moles per one mole of indium. A (average) size of the InPcore thus obtained is about 3.6 nanometers (nm).

Reference Example 2: InZnP cores are prepared in the following manner.

An InZnP core is prepared in the same manner as set forth in ReferenceExample 1 except that Zinc acetate is further used in an amount of onemole per one mole of the indium precursor. A (average) size of the InZnPcore thus obtained is about 2.1 nm.

Green Quantum Dots

Example 1

1. Synthesis of Quantum Dots and Characterization Thereof

(1) Selenium and sulfur are dispersed in trioctylphosphine (TOP) toobtain a Se/TOP stock solution and a S/TOP stock solution, respectively.

In a 200 mL reaction flask, zinc acetate and oleic acid are dissolved intrioctyl amine and the solution is subjected to vacuum at 120° C. for 10minutes. The atmosphere in the reaction flask is replaced with N₂. Whilethe resulting solution is heated to about 320° C., a toluene dispersionof the InZnP semiconductor nanocrystal core prepared in ReferenceExample 2 is injected thereto and a predetermined amount of Se/TOP stocksolution is injected into the reaction flask over three times. Areaction is carried out to obtain a reaction solution including aparticle having a ZnSe shell disposed on the InZnP core. A total ofreaction time is 100 minutes and a total amount of the Se as used perone mole of the indium is about 13 moles.

Then, at the aforementioned reaction temperature, the S/TOP stocksolution is injected to the reaction mixture. A reaction is carried outto obtain a resulting solution including a particle having a ZnS shelldisposed on the ZnSe shell. A total of reaction time is 40 minutes and atotal amount of the S as used per one mole of the indium is about 12moles.

An excess amount of ethanol is added to the final reaction mixtureincluding the resulting InZnP/ZnSe/ZnS semiconductor nanocrystals, whichis then centrifuged. After centrifugation, the supernatant is discardedand the precipitate is dried and dispersed in chloroform to obtain aquantum dot solution (hereinafter, QD solution).

(2) For the obtained QD solution, an ICP-AES analysis is made and theresults are shown in Table 1. A UV-vis absorption spectroscopic analysisand a photoluminescence spectroscopic analysis are made for the QDsolution, and the results are shown in Table 1.

2. Production of a Quantum Dot Polymer Composite and a Pattern Thereof

(1) Preparation of quantum dot-binder dispersion

A chloroform solution of the quantum dots prepared above is mixed with asolution of a binder polymer, which is a four membered copolymer ofmethacrylic acid, benzyl methacrylate, hydroxyethyl methacrylate, andstyrene, (acid value: 130 milligrams (mg) of KOH per gram (mg KOH/g),molecular weight: 8,000 g/mol, acrylic acid:benzylmethacrylate:hydroxyethyl methacrylate:styrene (molarratio)=61.5:12:16.3:10.2) (solvent: propylene glycol monomethyl etheracetate, PGMEA, a concentration of 30 percent by weight, wt %) to form aquantum dot-binder dispersion.

(2) Preparation of a photosensitive composition

To the quantum dot-binder dispersion prepared above, a hexaacrylatehaving the following structure (as a photopolymerizable monomer),ethylene glycol di-3-mercaptopropionate (hereinafter, 2T, as amulti-thiol compound), an oxime ester compound (as an initiator), TiO₂as a metal oxide fine particle, and PGMEA (as a solvent) are added toobtain a composition.

wherein

Based on a total solid content, the prepared composition includes 40 wt% of quantum dots, 12.5 wt % of the binder polymer, 25 wt % of 2T, 12 wt% of the photopolymerizable monomer, 0.5 wt % of the photoinitiator, and10 wt % of the metal oxide fine particle. The total solid content isabout 25%.

(3) Formation of quantum dot-polymer composite pattern and heattreatment thereof

The composition obtained above is spin-coated on a glass substrate at150 revolutions per minute (rpm) for 5 seconds (s) to provide a film.The obtained film is pre-baked at 100° C. (PRB). The pre-baked film isexposed to light (wavelength: 365 nanometers (nm), intensity: 100millijoules, mJ) under a mask having a predetermined pattern (e.g., asquare dot or stripe pattern) for 1 second (s) (EXP) and developed witha potassium hydroxide aqueous solution (concentration: 0.043 weight %)for 50 seconds to obtain a pattern of a quantum dot polymer composite(thickness: 6 micrometers (μm)).

The obtained pattern is heat-treated at a temperature of 180° C. for 30minutes under a nitrogen atmosphere (POB).

For the obtained pattern film, a photoluminescent peak wavelength, bluelight absorption rate, and a photoconversion efficiency are measured andthe results are shown in Table 1.

Examples 2 and 3

1. An InZnP/ZnSe/ZnS quantum dot of Example 2 is prepared in the samemanner as set forth in Example 1, except that per one mole of indium, atotal amount of the Se and a total amount of the S as used are 7 molesand 4.7 moles, respectively.

An InZnP/ZnSe/ZnS quantum dot of Example 3 is prepared in the samemanner as set forth in Example 1, except that per one mole of indium, atotal amount of the Se and a total amount of the S as used are 6 molesand 4 moles, respectively.

For the obtained QD solutions, an ICP-AES analysis, an UV-vis absorptionspectroscopic analysis and a photoluminescence spectroscopic analysisare made and the results are shown in Table 1.

2. A quantum dot polymer composite is prepared in the same manner as setforth in Example 1 except for using the quantum dots as obtained inthese Examples, respectively. For the obtained film pattern, blue lightabsorption rate, and a photoconversion efficiency are measured and theresults are shown in Table 1.

Comparative Example 1

An InZnP/ZnSe/ZnS quantum dot is prepared in the same manner as setforth in Example 1, except that per one mole of indium, a total amountof the Se and a total amount of the S as used are 6.4 moles and 26.3moles, respectively.

For the obtained QD solutions, an ICP-AES analysis, an UV-vis absorptionspectroscopic analysis and a photoluminescence spectroscopic analysisare made and the results are shown in Table 2.

A quantum dot polymer composite is prepared in the same manner as setforth in Example 1 except for using the quantum dots as obtained in thiscomparative example, respectively. For the obtained film pattern, bluelight absorption, and a photoconversion efficiency are measured and theresults are shown in Table 2.

Example 3-1 and Example 3-2

An InZnP/ZnSe/ZnS quantum dot of Example 3-1 is prepared in the samemanner as set forth in Example 1, except that per one mole of indium, atotal amount of the Se and a total amount of the S as used are 8 molesand 24moles, respectively.

An InZnP/ZnSe/ZnS quantum dot of Example 3-2 is prepared in the samemanner as set forth in Example 1, except that per one mole of indium, atotal amount of the Se and a total amount of the S as used are 8 molesand 18 moles, respectively.

For the obtained QD solutions, an ICP-AES analysis, an UV-vis absorptionspectroscopic analysis and a photoluminescence spectroscopic analysisare made and the results are shown in Table 2.

A quantum dot polymer composite is prepared in the same manner as setforth in Example 1 except for using the quantum dots as obtained inthese Examples, respectively. For the obtained film pattern, blue lightabsorption, and a photoconversion efficiency are measured and theresults are shown in Table 2.

TABLE 1 Exam- Exam- Exam- ple 1 ple 2 ple 3 450 nm:350 nm absorptionratio 0.090:1 0.102:1 0.110:1 Quantum Yield (QY) 85.3%   78%   80% Bluelight absorption rate 91.2% 92.2% 93.6% Photoluminescent Peak wavelength(nm) 541 531 536 ZnSe thickness (ML) 4 3 3 ZnS thickness (nm) 0.38 0.210.21 ICP S/Se (moles) 0.71 0.5 0.51 Zn:In (moles)   22:1   11:1    9:1

TABLE 2 Compar- Exam- Exam- ative ple ple Example 1 3-1 3-2 450 nm:350nm absorption ratio 0.049:1 0.064:1 0.079:1 Blue light absorption rate81% 84% 86% Photoluminescent Peak wavelength (nm) 536 538 538 ZnSethickness ((ML) 3 3 4 ZnS thickness ((nm) 0.97 0.83 0.75 ICP S/Se 3.112.22 1.69 Zn:In (moles)   49:1   40:1   31:1

The results of the table confirm that the quantum dots of Examples 1 to3 may exhibit enhanced optical properties and stability in comparisonwith the quantum dots of Comparative Example 1. The quantum dots ofExamples may have a 450 nm:350 nm absorption ratio of greater than orequal to about 0.08:1.

The film pattern of the quantum dot polymer composite including thequantum dots of Examples 1 to 3 may exhibit blue light absorption thatis significantly higher than that of the film pattern of the quantum dotpolymer composite including the quantum dots of Comparative Example 1.

Red Quantum Dots

Example 4

1. Synthesis of Quantum Dots and Characterization Thereof (1) Seleniumand sulfur are dispersed in trioctylphosphine (TOP) to obtain a Se/TOPstock solution and a S/TOP stock solution, respectively.

In a 200 mL reaction flask, zinc acetate and oleic acid are dissolved intrioctyl amine and the solution is subjected to vacuum at 120° C. for 10minutes. The atmosphere in the reaction flask is replaced with N₂. Whilethe resulting solution is heated to about 320° C., a toluene dispersionof the InP semiconductor nanocrystal core prepared in Reference Example1 is injected thereto and a predetermined amount of Se/TOP stocksolution is injected into the reaction flask over several times. Areaction is carried out to obtain a reaction solution including aparticle having a ZnSe shell disposed on the core. A total of reactiontime is 80 minutes and a total amount of the Se as used per one mole ofthe indium is about 6 moles.

Then, at the aforementioned reaction temperature, the S/TOP stocksolution is injected to the reaction mixture. A reaction is carried outto obtain a resulting solution including a particle having a ZnS shelldisposed on the ZnSe shell. A total of reaction time is 40 minutes and atotal amount of the S as used per one mole of the indium is about 9moles.

An excess amount of ethanol is added to the final reaction mixtureincluding the resulting InP/ZnSe/ZnS semiconductor nanocrystals, whichis then centrifuged. After centrifugation, the supernatant is discardedand the precipitate is dried and dispersed in chloroform to obtain aquantum dot solution (hereinafter, QD solution).

(2) For the obtained QD solution, an ICP-AES analysis is made and theresults are shown in Table 1. A UV-vis absorption spectroscopic analysisand a photoluminescence spectroscopic analysis are made for the QDsolution, and the results are shown in Table 3.

2. Production of a Quantum Dot Polymer Composite and a Pattern Thereof

A quantum dot polymer composite is prepared in the same manner as setforth in Example 1 except for using the quantum dots as obtained in thisExample. For the obtained film pattern, blue light absorption rate, anda photoconversion efficiency are measured and the results are shown inTable 3.

Examples 5 and 6

1. An InP/ZnSe/ZnS quantum dot of Example 5 is prepared in the samemanner as set forth in Example 4, except that per one mole of indium, atotal amount of the Se and a total amount of the S as used are 6 molesand 3 moles, respectively.

An InP/ZnSe/ZnS quantum dot of Example 6 is prepared in the same manneras set forth in Example 4, except that per one mole of indium, a totalamount of the Se and a total amount of the S as used are 3 moles and 3moles, respectively.

For the obtained QD solutions, an ICP-AES analysis, an UV-vis absorptionspectroscopic analysis and a photoluminescence spectroscopic analysisare made and the results are shown in Table 3.

2. A quantum dot polymer composite is prepared in the same manner as setforth in Example 1 except for using the quantum dots as obtained inthese Examples, respectively. For the obtained film pattern, blue lightabsorption rate, and a photoconversion efficiency are measured and theresults are shown in Table 3.

Examples 7 and 8

1. An InP/ZnSe/ZnS quantum dot of Example 7 is prepared in the samemanner as set forth in Example 4, except that per one mole of indium, atotal amount of the Se and a total amount of the S as used are 11 molesand 10 moles, respectively.

An InP/ZnSe/ZnS quantum dot of Example 6 is prepared in the same manneras set forth in Example 4, except that per one mole of indium, a totalamount of the Se and a total amount of the S as used are 11 moles and 7moles, respectively.

For the obtained QD solutions, an ICP-AES analysis, an UV-vis absorptionspectroscopic analysis and a photoluminescence spectroscopic analysisare made and the results are shown in Table 4.

2. A quantum dot polymer composite is prepared in the same manner as setforth in Example 1 except for using the quantum dots as obtained inthese Examples, respectively. For the obtained film pattern, blue lightabsorption, and a photoconversion efficiency are measured and theresults are shown in Table 4.

TABLE 3 Exam- Exam- Exam- ple 4  ple 5 ple 6 450 nm:350 nm absorptionratio 0.114:1 0.128:1 0.148:1 Blue light absorption rate 91.2%   93.1%  94.8%   Photoluminescent Peak wavelength (nm) 636 635 631 QY 87% 85% 92%ZnSe thickness (ML) 4 4 3 ZnS thickness (nm) 0.69 0.28 0.43 ICP S/Se1.19 0.4 1 Zn:In (moles)   12:1    8:1    6:1

TABLE 4 Example 7 Example 8 450 nm:350 nm absorption ratio 0.092:10.102:1 Blue light absorption rate 87% 88% Photoluminescent Peakwavelength (nm) 630 637 ZnSe (ML) 6 7 ZnS (nm) 0.58 0.40 ICP S/Se 0.710.49 Zn:In (moles)   17:1   16:1

The results of the table confirm that the quantum dots of Examples 4 to6 may exhibit enhanced optical properties and stability. The quantumdots of Examples may have a 450 nm:350 nm absorption ratio of greaterthan or equal to about 0.08:1.

The film pattern of the quantum dot polymer composite including thequantum dots of Examples 4 to 6 may exhibit improved blue lightabsorption rate, for example, of greater than or equal to about 89%,e.g., from about 91% to about 95%.

While this disclosure has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. Quantum dots comprising: a semiconductornanocrystal core comprising indium and phosphorous, a semiconductornanocrystal shell disposed on the semiconductor nanocrystal core, thesemiconductor nanocrystal shell comprising zinc, selenium, and sulfur,wherein the quantum dots do not comprise cadmium, and wherein thequantum dots are configured to emit green light having a luminescentpeak wavelength of from about 500 nanometers to about 550 nanometers,and the quantum dots comprise a molar ratio of zinc with respect toindium is less than or equal to 48:1 and greater than or equal to about3:1, or wherein the quantum dots are configured to emit red light havinga luminescent peak wavelength of from about 600 nanometers to about 650nanometers, and the quantum dots comprise a molar ratio of zinc withrespect to indium is less than or equal to about 30:1 and greater thanor equal to about 3:1.
 2. The quantum dots of claim 1, wherein thequantum dots are configured to emit green light and the quantum dotscomprise a mole ratio of zinc with respect to indium is less than orequal to 33:1 and greater than or equal to about 5:1.
 3. The quantumdots of claim 1, wherein a thickness of the second semiconductornanocrystal shell is less than 0.7 nanometers.
 4. The quantum dots ofclaim 1, wherein the quantum dots are configured to emit red light andthe quantum dots comprise a mole ratio of zinc with respect to indium isless than or equal to 28:1 and greater than or equal to about 4:1. 5.The quantum dots of claim 1, wherein the quantum dots comprises a moleratio of sulfur to selenium of less than or equal to about 2.5:1.
 6. Thequantum dots of claim 1, wherein the quantum dots are configured to emitthe green light and in a UV-Vis absorption spectrum of the quantum dots,a first absorption peak wavelength of the quantum dots is from about 450nm to about 520 nm; or wherein the quantum dots are configured to emitthe red light and in a UV-Vis absorption spectrum of the quantum dots, afirst absorption peak wavelength of the quantum dots is from about 580nm to about 620 nm.
 7. A display device, comprising a light emittingelement and optionally a light source, wherein the light emittingelement comprises the quantum dots of claim
 1. 8. A quantum dotcomposite film comprising a matrix and quantum dots dispersed in thematrix, wherein the quantum dots comprises a semiconductor nanocrystalcore comprising indium and phosphorous, and a semiconductor nanocrystalshell disposed on the semiconductor nanocrystal core, the semiconductornanocrystal shell comprising zinc, selenium, d sulfur, wherein thequantum dots do not comprise cadmium, and wherein the quantum dots areconfigured to emit green light having a luminescent peak wavelength offrom about 500 nanometers to about 550 nanometers, and the quantum dotscomprise a molar ratio of zinc with respect to indium is less than orequal to 48:1 and greater than or equal to about 3:1, or wherein thequantum dots are configured to emit red light having a luminescent peakwavelength of from about 600 nanometers to about 650 nanometers, and thequantum dots comprise a molar ratio of zinc with respect to indium isless than or equal to about 30:1 and greater than or equal to about 3:1.9. The quantum dot composite film of claim 8, wherein the quantum dotcomposite film comprises a first quantum dot composite disposed in afirst section, and a second quantum dot composite disposed in a secondsection wherein the first quantum dot composite comprises the quantumdots emitting the green light and is configured to emit green light andwherein the second quantum dot composite comprises the quantum dotsemitting the red light and is configured to emit red light.
 10. Thequantum dot film of claim 9, wherein the first quantum dot composite isconfigured to show a blue light absorption of greater than or equal toabout 90% with respect to blue light having a wavelength of about 450nm, and wherein the blue light absorption is defined as below: Bluelight absorption=[(B-B′)/B]×100% B is a blue light amount of an incidentlight B′ is a blue light amount passing the first quantum dot composite.11. The quantum dot film of claim 9, wherein in the first quantum dotcomposite, the quantum dots comprises a mole ratio of zinc with respectto indium is less than or equal to 33:1 and greater than or equal toabout 5:1, and wherein in the second quantum dot composite, the quantumdots comprises a mole ratio of zinc with respect to indium is less thanor equal to about 30:1 and greater than or equal to about 3:1.
 12. Astacked structure comprising a substrate and the quantum dot compositefilm of claim 8 disposed on the substrate.
 13. The stacked structure ofclaim 12, further comprising an optical element reflecting or absorbingblue light and optionally green light between the substrate and thequantum dot composite film.
 14. The stacked structure of claim 12,wherein the quantum dot composite film comprises a first quantum dotcomposite disposed in a first section, a second quantum dot compositedisposed in a second section, and optionally a black matrix between thefirst quantum dot composite and the second quantum dot composite,wherein the first quantum dot composite is configured to emit greenlight and the second quantum dot composite is configured to emit redlight.
 15. A display device, comprising a light emitting element andoptionally a light source, wherein the light emitting element comprisesthe quantum dot film of claim 8, and wherein the light source isconfigured to provide the light emitting element with incident light.16. The display device of claim 15, wherein the light source comprisesan LED, an organic light emitting diode, a micro LED, or a combinationthereof, and wherein the organic light emitting diode emits blue lightand optionally green light.
 17. The display device of claim 15, whereinthe display device further comprises a reflector, a prism sheet, adiffusion plate, or a combination thereof.
 18. The display device ofclaim 15, wherein the display device further comprises a liquid crystalpanel.
 19. The display device of claim 15, wherein the display devicefurther comprises a color filter disposed over the liquid crystal panel.20. The display device of claim 15, wherein the display device furthercomprises a first optical filter, a second optical filter, or acombination thereof, and wherein the first optical filter is configuredto block light having a wavelength of less than or equal to about 500nm; or wherein the second optical filter is configured to reflect lighthaving a predetermined wavelength.
 21. The display device of claim 20,wherein the second optical filter is configured to reflect light havinga wavelength of greater than 500 nm.
 22. The display device of claim 15,wherein the display device further includes an optical filter comprisinga plurality of layers stacked and having different refractive indicesfrom one another.